GEOLOGIJA 56/1, 057-072, Ljubljana 2013 doi:10.5474/geologija.2013.005
Opuščeni rudnik Remšnik z ramsbeckitom in namuwitom(?)
Abandoned Rem{nik mine with ramsbeckite and namuwite(?)
Mirka TRAJANOVA1 & Zmago ŽORŽ2
1Geolo{ki zavod Slovenije, Dimi~eva ulica 14, SI-1000 Ljubljana, e-mail: mirka.trajanova@geo-zs.si 2Pod Perkolico 52, 2360 Radlje ob Dravi, e-mail: zmago.zorz@gmail.com
Prejeto / Received 17. 4. 2013; Sprejeto / Accepted 8. 5. 2013
Ključne besede: ramsbeckit, namuwit, bakrovi, cinkovi in svin~evi sekundarni minerali, Rem{nik, Kobansko, severna Slovenija
Key-words: ramsbeckite, namuwite, secondary minerals of copper, zinc and lead, Rem{nik, Kobansko, north Slovenia
Izvle~ek
Polimetalno rudi{~e Rem{nik se nahaja na Kobanskem v severni Sloveniji. Mineralizacija nastopa v narivni coni med staropaleozojskimi nizkometamorfnimi kamninami Štalenskogorske formacije, Rem{ni{kega pokrova in retrogradno metamorfnih skrilavcev Avstroalpinske podlage. Hidrotermalno orudenje in okremenitev sledita skrilavemu klivažu v delno bre~iranih le~ah dolomitnih marmorjev ter podrejeno metatufitov in filitov. Najverjetneje je nastalo v povezavi z živahnim terciarnim magmatizmom, ki je ugotovljen in razkrit na obmo~ju dana{njega Pohorja. Mineralno paragenezo prevladujo~ega Pb, Cu, Zn srebronosnega sulfidnega orudenja spremlja pestra združba sekundarnih mineralov. Med njimi se nahajata pri nas prvi~ opisana redka vodna sulfata bakra in cinka. Zelene, prosojne monoklinske kristale, velikosti le nekaj desetink milimetra, smo z vrsti~nim elektronskim mikroskopom dolo~ili kot ramsbeckit (Cu, Zn)15(SO4)4(OH)22 • 6(H2O). Zelenkaste barve so tudi listi~asti, po obliki heksagonalni, cvetasti kristalni zra{~enci, ki najverjetneje pripadajo namuwitu (Cu, Zn)4(SO4)(OH)6 • 4(H2O). Zaradi submikroskopske velikosti in majhne koli~ine njegova dolo~itev {e ni zanesljiva.
Abstract
The polymetallic Rem{nik ore deposit is situated at the Kobansko area in northern Slovenia. Mineralization occurs in the thrust zone of the weakly metamorphosed old Palaeozoic rocks of the Magdalensberg formation, the Rem{nik nappe, onto the retrogressed schists of the Austroalpine metamorphic basement. Hydrothermal ore mineralization and silicification follow slaty cleavage in partly brecciated marmorized dolomite lenses and subordinately in metatuffites and phyllites. Its origin is most probably connected to the lively Tertiary magmatism, occurring at the Pohorje Mountains. Mineral paragenesis of the predominant Pb, Cu and Zn silver bearing sulphide ore is associated with numerous secondary minerals. Among them, two rare sulphates with H2O of Cu and Zn occur, found for the first time in Slovenia. The green, transparent monoclinic crystals, only some tenth of millimetre in size were determined by SEM as ramsbeckite (Cu, Zn)15(SO4)4(OH)22 • 6(H2O). Greenish in colour are also leafy, hexagonal, flowery intergrown crystals, which most probably belong to namuwite (Cu, Zn)4(SO4)(OH)6 • 4(H2O). Its submicro-scopic size and small quantity did not permit reliable determination, yet.
Uvod
Dosedanje raziskave Avstroalpinika pri nas so bile usmerjene predvsem na območje Pohorja, medtem ko so bili ostali deli vklju~eni v manj{em obsegu. Podrobno proučevanje mineralnih surovin in mineralogije je bilo pogosto postavljeno v ozadje. Zbiralski vnemi ljubiteljev mineralov se moramo zahvaliti, da se pri nas tudi na področju odkrivanja mineralov stvari premikajo naprej.
Čeprav je rudišče Remšnik znano že dolgo časa, spoznavanje njegove mineralne združbe še ni zaključeno. Za sledenje rudnih pojavov in s tem rudišč so pogosto prvi indikatorji sekundarni minerali, ki se pojavljajo v oksidacijskih conah.
Navadno najdemo le neznatne količine teh mineralov, vendar nam lahko kažejo, kaj se nahaja v njihovi okolici. Najdba ramsbeckita v remšniškem rudišču je zato pomembna tako z mineraloškega vidika, kot tudi z vidika sledenja sorodnih pojavov rudne mineralizacije na drugih območjih.
Remšnik danes kot rudno nahajališče ni več zanimiv, kljub temu pa predstavlja na širšem območju za strukturne geologe edini vpogled v tretjo dimenzijo, predvsem pa »Meko« za zbiralce redkih mineralov. Le-ti se radi pošalijo, da jih je Bog kaznoval z množico modrih in zelenih mineralov. Zato ni čudno, da tudi predstavljena najdba ramsbeckita pripada zelenim kristalčkom. Vendar pa so se že makroskopsko, še posebno pa pod lupo, razlikovali od do sedaj


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Sl. 1. Položaj vasi Remšnik in opuš~enega Jani~kovega rova. Izsek iz Google Earth. Fig. 1. Location of the Remšnik village and the abandoned Remšnik mine (Jani~ek pit). Cut out from Google Earth.
znanih v remšniškem rudiš~u. Njihova dolo~itev je predstavljala osnovo za pri~ujo~e raziskave.
Ramsbeckit so do sedaj, razen v matičnem nahajališču pri Ramsbecku in še nekaterih mestih v Nemčiji, našli v kar nekaj rudnikih po svetu: npr. v Italiji, prvič v rudniku »La Venezia« v limonitizira-ni jalovini (Orlandi & Perchiazzi,1989), o najdišču poročajo iz rudnikov Ecton v Pennsylvaniji (Pea-coR et al, 1987), Penrhiw (Mason & Green, 1995) in drugih iz Velike Britanije, z Japonske (Ohnishi et al, 2004) i.t.d. Po sedaj znanih podatkih so ga našli v enajstih državah na različnih lokacijah. Na mnogih mestih verjetno še čaka naključnega najditelja, saj ga pred tem dobro varuje obilica drugih zelenkastih mineralov in mikroskopska velikost kristalov.
Geografski položaj
Vzporedno s Pohorjem poteka na severni strani Dravske doline hribovje, ki ga uvrščamo med sredogorja. Ker nima enotnega pogorja, so ga v preteklosti večkrat neuspešno poskušali poimenovati enotno. V nekaterih atlasih je vpisano ime Kobansko, v drugih Kozjak. V osrednjem delu tega območja se v povirju levih pritokov reke Drave (Brezniškega, Štimpaškega in Vaškega potoka) nahaja raztreseno naselje Remšnik. Na zahodnem pobočju jugo-jugovzhodno potekajočega remšniškega hrbta, se južno od naselja nahaja opuščen rudnik Remšnik (sl. 1).
Od rudarskih objektov je najdostopnejši Janičkov rov, ki je označen na sliki 1. Območje je dokaj zaraščeno, zato ga prišlekom ni lahko najti.
Nekaj podatkov o rudišču
Rudišče Remšnik je pritegnilo pozornost raziskovalcev in rudarjev že pred več kot 250 leti. V
arhivskih virih (Arhiv R Slovenije) najdemo, da je baron Michelangelo Zois leta 1763 odprl rudnik in zgradil topilnico na Breznu, kar pomeni, da je bilo rudišče gotovo odkrito že prej, čeprav pisnih virov o tem nismo zasledili. Koncesija za odprtje rudnika je bila podeljena na podlagi fevdnega pisma z dne 14. junija 1850 pod št. 1937. Glasila se je na ime »Drauwalder silberhaltiger Blei, Kupfer und Zink Bergbau« (srebronosni svinčev, bakrov in cinkov rudnik Dravski gozd). Prvi lastniki rudnika so bili Jakob Krušnik, Karl Kranz in Johan Baumgartner. Izdelana sta bila dva rova, ki so ju poimenovali Marija in Franz, oz. tako imenovan Zwilling Stollen (dvojčični rov). V tem času so nakopano rudo talili v Ožbaltu ob Dravi. Po podatkih graške trgovinske zbornice so leta 1853 pridobili 74,658 kg srebra, tri leta kasneje le še okoli 50 kg. Oktobra 1887 je postal lastnik Karel Wehrkan iz Litije in ga že leta 1888 prodal Litijski rudarski družbi. Ta je prenehala z odkopavanjem rude na Remšniku 22. decembra 1891. V tem času so izkopali rov pod kmetijo Dijak in ga poimenovali Janičkov rov, rudnik pa »Fressen Bergbau«. Do druge svetovne vojne se je zamenjalo še nekaj lastnikov, dokler rudnik 1946. leta ni bil nacionaliziran. Po tem obdobju so ga obiskovali le geologi in zbiralci mineralov.
V remšniškem rudniku so namesto lesenega pod-porja uporabljali jalovinski material, s katerim so podzidali in podpirali rove in stene večjih odkopnih mest. Prav zato je Janičkov rov, kljub temu, da je le 3 do 5 m pod površjem, v sprednjem delu še danes dostopen, v zadnjem delu pa zarušen.
Po dosedanjih podatkih se orudenje v Remšniku nahaja v staropaleozojskih nizkometamorfnih kamninah Štalenskogorske formacije. Nastopa v obliki leč v območju metatufitov in dolomitnih marmorjev ter filitov (Drovenik et al, 1980). Najstarejši nam znani članek o rudišču predstavlja objava Tornqui-
Sl. 2. Tornquistova geolo{ka skica z ozna~enima rovoma Jani~ek in Ulbing pod narivnim stikom staropaleozojskih kamnin z retrogradno spremenjenimi in milonitiziranimi kamninami. Reproducirana slika 1 (iz: Tornquist, 1929). Fig. 2. Tornquist geological sketch with marked Jani~ek and Ulbing pits under the thrust contact of old-Paleozoic rocks with retrogressed and mylonitized rocks. Reproduced Figure 1 (From: Tornquist 1929).
sTa (1929), kjer omenja rudarska dela pod kmetijo Ulbing. Avtor je v svoji objavi na sliki 1 ozna~il dva rudniška rova (Janičkov in Ulbing) pod narivnim stikom staropaleozojskih kamnin (nem. altpaläozoische Sedimente) z retrogradno spremenjenimi in milonitiziranimi kamninami (nem. Mylonitdiaph-torite), ki je prikazana na sliki 2. Na manuskriptni geolo{ki karti odkopa pod kmetijo Dijak iz arhiva rudnika Mežica (Poro~ila geolo{ke službe rudnika Mežica, 1984-1989) uvrstitev kamnin med milonite ali prave filite ni opredeljena. Znana je le uvrstitev krovnih kamnin v Štalenskogorsko formacijo, ki sta jim Mioc in Ramovš (1973) na tem obmo~ju dolo~ila spodnjedevonsko starost. Zato {e vedno obstaja dvom, na katero formacijo (če je samo ena) je pravzaprav vezana mineralizacija.
O genezi rudi{~a so mnenja deljena. Orudenje nekateri povezujejo s pohorskim (Tornquist, 1929; DuHovNiK, 1956; Berce, 1963, Grafenauer, 1965), drugi pa s paleozojskim magmatizmom (Hegemann, 1960; Drovenik et al, 1980).
Polimetalno rudi{~e Rem{nik se pona{a z raznolikostjo mineralov, ki ji kar ni videti konca. Mineralno paragenezo sestavljajo {tevilni rudni in jalo-
vinski minerali, katerih skupno {tevilo že presega 55. Od rudnih mineralov so bili do sedaj določeni: galenit, sfalerit, pirit in halkopirit kot prevladujoči, podrejeno pa kuprit, tetraedrit, boulangerit, bornit, halkozin, covellin, freibergit, gersdorffit, akantit in polibazit. Drovenik (1980) in Grafenauer (1966) {e nista na{la polibazita in akantita, zato je Drovenik domneval, da je srebro (in bizmut) vgrajen v strukturi galenita in halkopirita. Posredno namiguje, da bi bila za visoko vsebnost srebra v galenitu lahko kriva tudi neustrezna analitska metoda.
Glavni jalovinski minerali v rudi so kremen, dolomit s povi{ano vsebnostjo železa in podrejeno kalcit in aragonit. Posebno pestrost pa predstavljajo sekundarni minerali, ki so nastali v oksidacijski coni rem{ni{kega rudi{~a. Naj na{tejemo le nekatere: kuprit, tenorit, hematit, goethit, manganovi oksidi in hidroksidi, malahit, azurit, smithsonit, cerusit, hidrocinkit, brianyoungit, rosasit, aurikal-cit, barit, sadra, linarit, langit, baverit, posnjakit in karbonatni cianotrihit, aragonit, piromorfit in kri-zokola (chrysocolla).
Nekaj pogostej{ih mineralov Kobanskega (predvsem kristale kremena) so prikazali žorž in sodelavci (2007).
Material in metode preiskav
Prikazani rezultati temeljijo tako na terenskih opazovanjih, kot tudi laboratorijskih preiskavah. Vzorci so bili odvzeti ob orudeni žili iz Janičkovega rova. Pestrost sekundarnih mineralov, ki se nahajajo v razpokah, lahko vidimo pod stereolupo, vendar so premajhni za določitev. Količina najdenih vzorcev ni bila zadostna, niti pa primerna za izdelavo petrografskih preparatov in/ali obrusov, saj bi tanke prevleke z bru{enjem izgubili. Izdelana je bila rentgenska difraktometrijska analiza na ko{čku vzorca z mikrokristalnim oprhom. Drobnih kristalčkov, ki smo jih želeli določiti, prav tako ni bilo mogoče izolirati za kemično analizo. Tako je od palete preiskovalnih metod, zaenkrat ostala le preiskava z vrstičnim elektronskim mikroskopom. Analize so izdelane s SEM znamke JEOL JSM 6490LV pri pospe{evalni energiji 20 kV, na delovni razdalji 10 mm. Uporabljen je na~in BSE pri nizkem vakuumu, brez napra{evanja. Osnovna semikvantitativna kemična sestava je določena z Oxford INCA EDS (compo način) pri enaki pospe{evalni energiji.
Rezultati in diskusija
Na Osnovni geolo{ki karti 1:100 000, list Slovenj Gradec (Mioc & žnidarčič, 1977) je rem{ni{ko nahajali{če označeno med Rem{ni{kim pokrovom iz {talenskogorskih kamnin in talninsko Pohorsko formacijo iz retrogradno metamorfnih skrilavcev Avstroalpinske podlage. Med njima se nahaja tanek pas filitov. Določitev filitov na tem območju in vzhodno od tod je nekoliko sporna. Zaradi
vecfaznih sekundarnih sprememb ni jasno, ali pripadajo pravim filitom ali pa milonitom, ki so nastali retrogradno iz dinamometamorfno spremenjenih kamnin Pohorske formacije (po Miocu, 1978 imenovane Kobanska serija). Nesporno je vanje vključenih tudi del {talenskogorskih kamnin, zajetih v narivno cono.
Tako makro-, kot tudi mikroteksture kamnin nakazujejo več faz tektonskega delovanja, vključno z dvakrat reaktiviranim subhorizontalnim strižnim premikanjem, zaradi katerega so v vse kamnine vtisnjene dinamometamorfne spremembe. Prvo se odraža kot plastične deformacije z nastankom fo-liacije. Pri tem so bile kamnine intenzivno miloni-tizirane. Pri drugem pa je nastal skrilav klivaž, ki pretežno sledi foliaciji. Nastanek teh struktur je v {ir{em območju vzhodnega Avstroalpinika povezan
Sl. 3. Razpoke in sekundarni klivaž nakazujejo delovanje desnega striga (rdeče puščice). Janičkov rov daje zavetje netopirjem. Opuščen rudnik Remšnik. Foto Z. Žorž. Fig. 3. Fractures and secondary cleavage indicate dextral sense of shear (red arrows). The Janiček ^it gives shelter to bats. Abandoned Remšnik mine. Photo Z. Žorž.
z zgornjekrednim krovnim narivanjem in terciarnim vzhodno usmerjenim alpskim pobegom (npr. FODOR et al. 1998, 2002, 2008). Strukturni parametri širšega območja nakazujejo, da sta bila Pohorje in Kobansko/Kozjak ob vtiskanju granodioritne magme v spodnjem miocenu še enoten blok in sta se ločila šele pozneje.
Stopnja dosedanjih raziskav ne dovoljuje enoznačne opredelitve geneze rudišča. Kljub temu pa se nakazujejo nekatere pomembne povezave, ki negirajo njegovo paleozojsko poreklo: sulfidna rudna mineralizacija in močna okremenitev, ki je prikrila teksturni značaj kamnin, sta sledili klivažu, ki je terciarnega (predvidoma miocenskega) nastanka; kobanski blok se je ločil od pohorskega verjetno v srednjem miocenu in je bil do tedaj bliže vplivnemu območju granodioritne intruzije; mineralna sestava in izotopska sestava žvepla v Remšniku in na Okoški gori na Pohorju sta sorodni (Drove-NiK et al. 1976, 1980). Na osnovi tega obstaja velika verjetnost, da je orudenje povezano z miocenskim pohorskim magmatizmom, kot so že domnevali ToRNQuisT (1929), DuHovNiK (1956), Berce (1963) in Grafenauer (1965). Še vedno pa ostaja vprašanje, ali je lahko povezano tudi z remobilizacijo starejše (kredne/paleozojske?) mineralizacije, saj naj bi po Droveniku in sodelavcih (1980) orudenje na Okoški gori nastalo v paleozoiku. To starost argumentirajo z blastično rastjo rudnih mineralov v času regionalne metamorfoze, kar pa ni zadosten razlog.
Prečno na foliacijo in skrilav klivaž potekajo mlajše poševne razpoke, nastale kot posledica obnovljenega strižnega premikanja. Oblikujejo sekundarne klivažne ravnine ter označujejo delovanje desnega striga (sl. 3). Te razpoke niso okremenjene in so brez primarne (sulfidne) mineralizacije. Vse
Sl. 4. Delno zarušen Janičkov rov. Vidne so subhorizontal-ne razpoke vzporedne starejšemu klivažu in strma prelomna površina (zgoraj). Levo spodaj je odlomljen blok brečiranega in nato še močno okremenjenega dolomita. Janičkov rov, opuščen rudnik Remšnik. Foto Z. Žorž.
Fig. 4. Partly collapsed Janiček pit. Subhorizontal fractures are parallel to the older cleavage. Steep fault surface (top of the figure) cut other structures. Fallen block of brecciated and subsequently strongly silicified dolomite can be seen at the bottom left. Abandoned Remšnik mine. Photo Z. Žorž.
Sl. 5. Modrikasti in zeleni oprhi sekundarnih mineralov na prečnih prelomnih površinah. Vzdolž klivaža po foliaciji se nahaja predvsem sulfidno svinčevo, cinkovo, bakrovo oru-denje in okremenitev (sveži odlomi v sredini slike). Remšnik, Janičkov rov. Foto Z. Žorž.
Fig. 5. Bluish and green coatings of secondary minerals on transverse fault plains. Prevailingly sulphide copper zinc and lead ore mineralization and silicification occur along the cleavage parallel to foliation (fresh surfaces in the photo centre). Janiček pit, abandoned Remšnik mine. Photo Z. Žorž.
Sl. 6. Rjavi (na levi skoraj ~rni) do 1 mm veliki kristali be-averita na kremenu iz Janičkovega rova. Opuščen rudnik Rem{nik. Najdba in zbirka Z. Žorž. Foto: B. Moser.
Fig. 6. Brown (nearly black on the left), up to 1 mm big crystals of beaverite on quartz from the Janiček pit. Abandoned Rem{nik mine. Find and collection Z. Žorž, photo B. Moser.
Sl. 7. Modri rosasit ter brezbarvni in prozorni aragonitni ježki iz Janičkovega rova. Opuščen rudnik Remšnik. Velikost motiva 15 x 12 mm. Najdba, zbirka in foto Z. Žorž.
Fig. 7. Blue rosasite and colourless transparent aragonite needles from the Janiček pit. Abandoned Remšnik mine. Size of the motif 15 x 12 mm. Find, collection and photo Z. Žorž.
strukture sekajo genetsko najmlaj{i subvertikalni prelomi (sl. 4) prevladujo~e smeri jugozahod-seve-rovzhod, redkeje pre~no nanje.
Razmere v Jani~kovem rovu kažejo, da so orude-ne pretežno karbonatne le~e ter delno {ir{a poru{ena narivna cona, v kateri so zajete tako kamnine Šta-lenskogorske, kot tudi Pohorske formacije. Primarna rudna mineralizacija in okremenitev sta sledili razpoklinski poroznosti starejšega skrilavega kliva-ža, ki makroskopsko sovpada s foliacijo, medtem ko v dveh generacijah pre~nih razpok in prelomov najdemo v glavnem sekundarno mineralizacijo (sl. 5). Bre~irane kamnine so prepojene s kremenico, zato so na videz masivne.
Večino redkih sekundarnih mineralov je na Rem{niku na{el Z. Žorž in dolo~il skupaj z Moser-jem (ŽoRž & Moser, 2002). Med njimi je posebno zanimiv beaverit, svinčev-bakrov-železov-aluminijev sulfat. Po dosegljivih podatkih je bil ta mineral do najdbe Z. Žorža poznan le kot rumen oprh, tu pa se nahajajo milimetrski, karamelno rjavi, prozorni do prosojni kristali (sl. 6). Nastopa kot prevleke na kremenu.
Med karbonati je zelo slikovita parageneza rosasita in aragonita na nekoliko limonitizirani kreme-novi podlagi (sl. 7).
V osnovi nekaterih sekundarnih mineralov smo s SEM določili hemimorfit (h) s kemično formulo (Zn4Si2O7(OH)2 ■ (H20). V vzorcih je tako mikrozrnat, da je tudi z vrstičnim elektronskim mikroskopom vidna le njegova skorjasta (natečna) struktura. Na SEM sliki 8 (levo) se nahaja ob kristalih ramsbeckita. EDS spekter hemimorfita (slika 8 desno) prikazuje glavne elemente kemične sestave Zn, Si in O.
Redki minerali, določeni v remšniškem rudišču, nastopajo v sledovih in so mikroskopske do submi-kroskopske velikosti, zato so do zadnjih nekaj let ostali neopaženi. Med njimi sta dve posebno lepi obliki sulfatov, ki pri nas do nedavna še nista bili najdeni. Gre za sekundarna minerala, ki nastajata v procesu pripovršinskega preperevanja bakro-
Sl. 8. Majhno svetlo sivo polje hemimorfita (h) ob dveh kristalih ramsbeckita. SEM posnetek (levo, izsek iz slike 13) in EDS spekter hemimorfita (zgoraj). Opuščen rudnik Remšnik.
Fig. 8. Small light grey field of hemimorphite (h) near two ramsbeckite crystals. Left - SEM (BSE) image (cut from fig. 12); top - EDS spectrum of hemimorphite. Abandoned Remšnik mine.
vo cinkovih rud, odvalov in žlinder. Prvi pripada ramsbeckitu, ki sta ga na kratko predstavila ŽoRž in Trajanova (2010).
Dolo~itev drugega minerala je {e vedno vpra{ljiva, saj nastopa v neznatni koli~ini in v tako drobnih kristalih, da ga pod binokularno lupo nismo opazili in ga tudi s SEM analizo nismo uspeli enozna~no dokazati. Njegova semikvantitativna kemi~na sestava in kristalna oblika pa nakazujeta, da zelo verjetno pripada namuwitu.
Ramsbeckit
Zna~ilne rudne žile v rem{ni{kem rudi{~u so sestavljene predvsem iz halkopirita, galenita in sfale-rita v osnovi iz kremena in karbonatov, od katerih je najpogostej{i dolomit. V opu{~enih rovih dosežejo v povpre~ju debelino med 3 in 5 cm. Debelej{e žile so navadno sestavljene iz ve~ slojev, ki so med seboj lo~eni s trakovi kremena in dolomita. Slednji je videti kot pole razlistane osnovne kamnine in/ali pa remobiliziranega karbonata iz nje. Sekundarna mineralizacija se nahaja v odprtih razpokah in prelomih. Razpoke sekundarnega klivaža položno, vzdolžno sekajo rudne žile. V naj mlaj {ih, strmih prelomih in razpokah so se kot oprhi odlagali le sekundarni minerali, zna~ilni za oksidacijsko cono.
Debelej{a orudena žila z ramsbeckitom se nahaja v spodnjem (drugem) obzorju, ki je okrog 7 m pod povr{jem. Sestavljena je predvsem iz halkopirita, galenita in sfalerita. Med posameznimi sloji v žili je kristaliziral pirit, ki ima razvite kristalne ploskve pentagonskega dodekaedra, velikosti do enega milimetra. Oprhi bakrovo cinkovih sekundarnih mineralov so se odložili v razpoki v zgornjem delu žile. Razpoka v sredini žile je vsebovala najve~ linarita in langita. V spodnjem delu žile so prevladovali kristali malahita in rosasita v združbi z redkima auri-halkitom in hidrocinkitom.
Kljub ve~anju {tevila najdb, ramsbeckit {e vedno spada med redke sulfate. Po Nickel-Strunzovi klasifikaciji mineralov spada med vodne sulfate z dodatnimi anioni, v prostorsko skupino P 21/a 2/m. Mati~no nahajali{~e je rudnik Bastenberg blizu kraja Ramsbeck v Nem~iji, po katerem je dobil svoje ime. Odkrit je bil leta 1984, IMA pa ga je potrdila 1985 (Internet 1). Prvi so ga opisali Hodenberg in sodelavci leta 1985 in zanj podali stehiometri~no kemijsko formulo (Cu, Zn)7(SO4)2(OH)10-5(H2O). Dolo~ili so mineralno paragenezo (Hodenberg et al. 1985), ki je povsem primerljiva z rem{ni{ko. Kristalno zgradbo je leta 1988 dolo~il Effenberger. Revidiral je kemijsko formulo in jo iz prej{nje oblike popravil v (Cu,Zn)15(SO4)4(OH)22-6(H2O).
Ramsbeckit iz Jani~kovega rova nastopa v pravilnih kristalih, velikih nekaj desetink mm, najve~ do 0,5 mm, ki so makroskopsko vidni le kot barvne prevleke (sl. 9). Pri pove~ani fotografiji so lokalno že prepoznavni nejasni, živo zeleni kristali (sl. 10). Pod binokularno lupo imajo zeleno barvo, vendar
zaradi mo~ne refleksije od kristalnih ploskev, fotografije niso bile uspe{ne. Za bolj{o predstavo barve minerala je ustrezna fotografija ramsbeckita iz nahajali{~a Penrhiw na Walesu, prikazana na spletni strani (Internet 2 ali Internet 3), ki povsem odgovarja primerkom iz Rem{nika. Kristali so prosojni in imajo nekoliko svileno steklast sijaj. Na vzorcu, ki je bil shranjen v suhem prostoru, so kristali nekoliko izgubili zeleno barvo, medtem ko je modrikasta niansa postala izrazitej{a.
Ramsbeckit kristalizira v monoklinskem sistemu. Kristali so razli~nih oblik. Najizrazitej{a je ploskev osnovnega pinakoida (001), po katerem je vidna nejasna razkolnost. Izraziti sta ploskvi (100) in (010). Ploskev (210) je praviloma manj{a od ostalih (sl. 11), medtem ko se ploskvi (120) in (310) v ve~ini primerov sploh nista razvili (sl. 12, v sredini). V nekaterih kristalih pa so razvite le ploskve (100), (001) in (010) (sl. 12, levo spodaj in desno zgoraj).
Skice idealiziranih oblik kristalov ramsbeckita, ki smo jih na{li do sedaj, so prikazane na sliki 13. Na sliki 13 B so z indeksi ozna~ene kristalne ploskve oblik 1, 2 in 3 s slike 13 A. Kristalne ploskve, ki dolo~ajo morfologijo ramsbeckita so pinakoidi (001), (100), (010) in (210) ter prizma 3. reda (110) (slika 13, risbi 2A, 2B). Prizma (110) je lahko bolj, ali manj izrazita. Kristali ramsbeckita imajo lahko razvite samo kristalne ploskve pinakoidov (slika 13,
Sl. 9. Modrikasto zelene prevleke prevladujočih sulfatnih sekundarnih mineralov z ramsbeckitom iz Janičkovega rova. Opuščen rudnik Remšnik. Foto M. Trajanova.
Fig. 9. Bluish green coatings of predominant sulphate minerals with ramsbeckite from Janiček pit. Abandoned Remšnik mine. Photo M. Trajanova.
Sl. 10. Zeleni kristali ramsbeckita iz Janičkovega rova. Redka modra zrna so langit. Opuščen rudnik Remšnik. Foto M. Demšar. Fig. 10. Bright green crystals of ramsbeckite from Janiček pit. Blue grains belong to langite. Abandoned Remšnik mine. Photo M. Demšar.
Sl. 11. Kristalni zra{~enci ramsbeckita z lepo vidnimi ploskvami osnovnega pinakoida in prizem. SEM (BSE) posnetek.
Fig. 11. Intergrown ramsbeckite crystals with expressed plains of basal pinacoid and prisms. SEM (BSE) image.
risba 1A, 1B). Najpogostej{a je oblika 2, pri kateri je lahko ploskev (010) kraj{a, na ra~un podalj{ane ploskve (210), kot je primer oblika 2 na sliki 13A. Najpestrejša in redkejša je oblika 3, ki ima razvitih največ kristalnih ploskev. V tem primeru je ploskev (110) lomljena, tako da se je razvila ploskev (120). Tudi ploskev (010) je lomljena in na njen ra~un je nastala ploskev (310) (sl. 13, oblika 3A, 3B). Primer te oblike vidimo na sliki 11 na spodnji desni polovici najve~jega kristala osrednjega zra{~enca.
Sl. 12. Dve zrni ramsbeckita v sredini predstavljata najpogostej{o obliko s ploskvami (001), (100), (110), (010) in (210). Levo spodaj in desno zgoraj sta kristala z razvitimi pi-nakoidi. SEM posnetek.
Fig. 12. Two grains in the figure centre represent the most frequent form with planes (001), (100), (110), (010) and (210). Crystals with developed pinacoids can be seen at the bottom left and top right. SEM (BSE) image.
Peacor in sodelavci (1987) in Ohnishi in sodelavci (2004) omenjajo razkolnost ramsbeckita po osnovnem pinakoidu, ki je nakazana tudi v na{em primeru (slika 11, na osrednjem zra{~encu, zgoraj). Vi{ji kristal 4 (sl. 13A) najverjetneje predstavlja dvoj~ek. Kot zasledimo v Mineralo{kem priro~niku, verzija 1 (Bideaux & Nichols, 2004, ©
Sl. 13. Skica do sedaj najdenih kristalnih oblik ramsbeckita v opuščenem rudišču Remšnik. Glej razlago v tekstu.
Fig. 13. Sketch of the so far found ramsbeckite crystal forms in the abandoned Remšnik mine. See explanation in the text.
Sl. 14. EDS spekter ramsbeckita (leva točka na sliki levo).
Fig. 14. EDS spectrum of ramsbeckite (left spot in the left figure).
Sl. 15. EDS spekter čiste površine zrna ramsbeckita vidnega
na desni strani na sliki 12.
Fig. 15. EDS spectrum of clear ramsbeckite grain surface seen at the right side of figure 12.
2004-2013), ima ramsbeckit ponavljajoče dvojčke, ki oblikujejo cilindrične skupke. Tak primer bi lahko predstavljal kristal na SEM posnetku (sl. 14 levo). Podobnost nekaterih oblik kristalov z remšniškimi (np. oblika 1 s slike 13A, 13B) vidimo na sliki 1 OHNisHi-ja in sodelavcev (2004) iz rudnika Hirao blizu Osake na Japonskem, kjer prevladujejo na videz romboedrski kristali.
Kvalitativna kemična sestava ramsbeckita je prikazana na EDS spektru (sl. 14 desno). Zaradi drobnih zrnc na površini kristala se pojavi neznaten pik Si. Za ploščati ramsbeckit nenavadno visok kristal verjetno predstavlja dvojček, ki je enak obliki 4 na sliki 13 A.
EDS spekter čistega ramsbeckita (sl. 15) je sne-man na čisti, gladki površini spodnjega kristala ob zgornjem desnem robu slike 11. V sestavi zato ni primesi silicija, kot na EDS spektru na sliki 14.
Po kemični sestavi je ramsbeckitu sorodnih kar nekaj redkih mineralov sulfatov, kot na primer: lan-git, posnjakit, wroewolfeit, spangolit, ktenasit, pa tudi namuwit.
Na rentgenskem difraktometru smo poskusili snemati košček vzorca z mikrokristalnim oprhom, vendar analiza ni bila uspešna.
Namuwit
V sestavi modrikasto zelenih, na oko amorfnih oprhov, se v razpokah ob ramsbeckitu nahaja še en mikrokristalen sekundarni sulfatni mineral, ki smo ga zaenkrat določili kot namuwit.
Namuwit so prvič opisali Bevins in sodelavci leta 1982. Določen je bil v vzorcu iz rudišča Aberllyn, ki se nahaja v zbirki Narodnega muzeja na Walesu, po katerem je dobil ime (NAtional MUseum of Wales). Istega leta ga je potrdila IMA (Internet 4). Leta 1983 je bil na kratko prikazan tudi v reviji American mineralogists pod »New mineral names« (Fleischer & Pabst, 1983). Od tedaj dalje so ga našli na številnih mestih po svetu, tako v oksidacijskih conah bakrovo cinkovih rudišč, kot tudi na rudniških odvalih, največkrat v paragenezi z ramsbeckitom.
Kemijska formula namuwita je (Cu, Zn)4(SO4) (OH)6^4(H2O) (Bevins et al., 1982). Avtorji ga opisui-jejo kot svetlo morsko zelen mineral z bisernim si-
jajem. Ker je v začetnih raziskavah upoštevana le kemična sestava, določena na SEM EDS, smo ga prišteli k ramsbeckitu (Žorž & Trajanova, 2010). Zaradi oblike kristalov s šesterokotnimi preseki, podobnimi sljudam, je bila določitev dvomljiva, zato smo s SEM naredili dodatne raziskave. Skupaj z ramsbeckitom smo ga poskušali določiti tudi z rentgensko difrakcijo, vendar neuspešno. Z EDS dobljena kvalitativna kemična sestava je enaka kot za ramsbeckit. Semikavntitativna kemična sestava pa se nekoliko razlikuje, čeprav je zaradi uporabe ne-poliranega vzorca in premajhnih zrnc nezanesljiva.
Po obliki rozet je namuwit zelo podoben še enemu sulfatu, posnjakitu, razlikuje pa se po barvi (posnjakit je moder, namuwit bledo zelen) in kemični sestavi, ker vsebuje poleg bakra tudi cink. Na osnovi tega in oblike kristalov sklepamo, da mineral naj-
Sl. 16. Ob zraščencu ramsbeckita se nahajajo drobni kristalni skupki namuwita (?), ki kažejo šesterokotno simetrijo. SEM (BSE) posnetek.
Fig. 16. Tiny crystal clusters of namuwite (?), showing hexagonal symmetry, are seen beside ramsbeckite. SEM (BSE) image.
verjetneje pripada namuwitu. Značilni svetlo zeleni, submikroskopski cvetasti skupki namuwita (sl. 16) na skorjastih prevlekah sorodne kemične sesta-
Sl. 17. Cvetasto preraščanje heksagonalnih ploščic namuwita. SEM (BSE) posnetek.
Fig. 17. Flowery intergrowing of hexagonal plates of namuwi-te. SEM (BSE) image.
ve ob ramsbeckitu so enaki oblikam, ki so jih opisali Bevins in sodelavci (1982) in Groat (1996). Po njihovih podatkih je namuwit izomorfen s sintetičnim cinkovim sulfatom (Zn4SO4OH)2-4H2O).
Kristali rastejo iz pretežno amorfne podlage in redko presegajo velikosti 50 pm, izjemoma pa dosežejo tudi 80 pm. Imajo izrazito razkolnost po ploskvah osnovnega pinakoida (001). Pogosti so primeri prečnega preraščanja lističev, kot je vidno na slikah 16 (ob levem robu) in 17.
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Sl. 18. EDS spektra namuwita s slike 17.
Fig. 18. EDS spectra of namuwite from figure 17.
Kvalitativna kemična sestava remšniškega na-muwita s slike 17 je prikazan na sliki 18. Tako kot ramsbeckit, pripada bakrovemu cinkovemu vodnemu sulfatu z dodatnimi anioni. Zaradi neugodne lege kristalnih ploskev glede na lego detektorja, imajo piki spektra nesorazmerno velikost.
Kristalno strukturo namuwita je določil Groat (1996). Sestavljen je iz ponavljajočih slojev tetraeder-oktaeder-tetraeder (T-O-T), ki so z vodikovo vezjo povezani z medslojno H2O. Isti avtor je ugotovil, da je namuwit podvržen procesom hidracije in de-hidracije, odnosno prehodom iz tetrahidrata v pen-tahidrat in obratno, pri približno sobni temperaturi.
Zakljucek
Polimetalno orudenje v Remšniku je nastalo vzdolž klivažnih razpok sovpadajočih s foliacijo, kar nakazuje njegovo terciarno starost in zelo verjetno povezanost s pohorskim magmatizmom. V procesu oksidacije in pripovršinskega prepereva-nja primarne sulfidne mineralizacije so v mlajših razpokah kristalizirali številni sekundarni mine-
rali, med katerimi najdemo tudi zelo redke vrste. Pri nas sta to prvič opisana bakrovo cinkova sulfata ramsbeckit in namuwit. Določitev slednjega še ni enoznačna, zato upamo, da bo naslednja najdba količinsko bogatejša in bo omogočila uporabo analitskih tehnik, s katerimi bomo potrdili ali ovrgli sedanjo določitev.
Zahvala
Raziskave je finančno podprla Agencija za raziskovalno dejavnost Republike Slovenije v okviru raziskovalnega programa P1-0025, Sedimentologija in mineralne surovine. Zahvaljujeva se recenzentoma za koristne pripombe in popravke ter dr. Milošu Milerju za pomoč pri delu s SEM.
Abandoned Remšnik mine with ramsbeckite and namuwite(?)
Introduction
The investigations of the Austroalpine in Slovenia have been focused mostly on the area of Pohorje, while other areas have been included to a lesser extent. Detailed study of mineral deposits and mineralogy has usually been left aside. It is the enthusiasm of mineral collectors we have to thank that things are moving forward also in the area of mineral finds in Slovenia.
Though the Remšnik ore deposit has been known for a long time, the recognition of its mineral association is still not finished. Secondary minerals in the oxidation zones are frequently first indicators for tracing ores. Only insignificant quantities of these minerals are usually found, but they indicate what might occur in the surroundings. The find of ramsbeckite in the Remšnik ore deposit is therefore important from mineralogical point of view and also for tracing of cognate ore mineralization in other regions.
Remšnik is nowadays not of interest as an ore deposit; nevertheless, it represents the only insight into the third dimension in this region to structural geologists and particularly a "Mecca" for rare minerals collectors. The latter often like to joke that God punished them with a vast number of blue and green minerals. It is thus not surprising that also the presented ramsbeckite find belongs to green crystals. Despite the fact, they differ macroscopically and particularly under the hand lens from the so far known minerals in the Remšnik ore deposit. Their determination is the basis for the presented study.
Ramsbeckite has been already found in several mines around the world beside the parent occurrence near Ramsbeck in Germany, e.g.: in limonitic gangue in »La Venezia« mine for the first time in Italy (Orlandi & Perchiazzi, 1989), it is reported from Ecton mine in Pennsylvania (Peacor et al, 1987), from Penrhiw mine (Mason & Green, 1995)
and other locations in Great Britain, from Japan (ÜHNiSHi et al., 2004) etc. As for known data, it was found on different locations in 11 countries up to now. In other localities, it is probably still waiting for a coincidental finder, as it is well hidden among numerous other greenish minerals and by its microscopic crystal size.
Geographic setting
Parallel with the Pohorje Mountains and north of the Drava valley, a hilly area extends in northern Slovenia. As it has no continuous mountain chain, several attempts were made in the past to name the area with one name. The name Kobansko appears in some topographic maps and in the others Koz-jak. In the central part of this region, drained by the Brezni{ki, Štimpa{ki and Va{ki brooks, the scattered village of Rem{nik is situated. On the western slopes of the south-southeast trending Remshnik ridge, abandoned Remshnik mine (Janiček pit) occurs south of the village (Fig. 1).
Janiček pit marked in Figure 1 is the most accessible mining object. Its surrounding is densely vegetated and therefore not easy to be found.
Some data about the Rem{nik ore deposit
The Rem{nik ore deposit first attracted attention of researchers more than 250 years ago. We can read in documents stored in the Archive of Slovenia that count Michelangelo Zois opened the mine in 1763 and constructed a smelter in Brezno by the Drava River. This shows that the deposit had been discovered much earlier, though we could find no written sources to support this theory. A concession for the mine opening has been vested on the base of feudal letter dated June 14th 1850, under No. 1937. It was worded under the name »Drau-walder silberhältiger Blei, Kupfer und Zink Bergbau« (silver bearing lead, copper and zinc mine Drava forest). The first owners of the mine were Jakob Kru{nik, Karl Kranz and Johan Baumgartner. Pits were named Maria and Franz, or the Zwilling Stollen (the twin pit). At that time, the produced ore had been melted in the village of Ožbalt by the Drava River. According to the data of the then Graz Chamber of Commerce 74.66 kg of silver was extracted in 1853 and only about 50 kg three years later. In October 1887, Karel Wehrkan from Litija became the owner of the mine and as soon as in 1888 he sold it to the Litija Mining Company. They stopped with exploitation of ore in Rem{nik on December 22nd, 1891. In the meantime, they excavated a pit near the Dijak farm and named it Jani~ek pit and the mine itself »Fressen Bergbau«. Until the Second World War, the ownership of the mine had changed several times. It was nationalized in 1946 and afterwards only geologists and mineral collectors entered the pits.
In the Rem{nik mine, gangue material was used to support the pit walls instead of wooden pillars. Walls of the pits and bigger excavated spaces have been underpinned by blocks of country rock, which is why the Janiček pit is still accessible today in the front part, though only 5 to 7 m below the surface. It is collapsed in the back part.
According to the available data, ore mineralization in the Rem{nik mine occurs in the old Palaeozoic low metamorphic rocks of the Magdalens-berg formation. The mineralized bodies form lenses in metatuffs, dolomitic marbles and phyllites (Drovenik et al. 1980). The oldest known publication about the mine is the one by Tornquist (1929), where he mentioned mining works below the Ul-bing farm. He designated two mine pits in his Figure 1 (Janiček and Ulbing) below the thrust contact of old Palaeozoic rocks (altpaläozoische Sedimente) with retrogressed and mylonitized rocks (Mylonit-diaphtorite), shown in Figure 2. The manuscript geological map of the exploitation pit below the Dijak farm, kept at the Mežica mine Archive (Reports of the geological service, 1984-1989) contains no distinction between mylonites and phyllites. Consequently, it is still not clear, which formation (if it is only one) the mineralization is connected to. Only hanging wall rocks are pertained to Magdalensberg formation to which MioC and Ramovš (1973) determined Lower Devonian age in the Rem{nik area.
There are different opinions about the Rem{nik ore deposit genesis. Some researchers connect the mineralization to the Miocene Pohorje magmatism (Tornquist, 1929;Duhovnik, 1956; Berce, 1963, Grafenauer, 1965), others to the Palaeozoic mag-matism (Hegemann, 1960; Drovenik et al. 1980).
The Rem{nik polymetallic ore deposit prides itself on variety of minerals. The mineral paragenesis consists of numerous ore and gangue minerals, together exceeding 55 types. The following ore minerals have been determined: ga-lenite, sphalerite, pyrite and chalcopyrite as the prevailing types, and subordinately cuprite, tetra-hedrite, boulangerite, bornite, chalcosine, covel-line, freibergite, gersdorffite, acanthite and poly-basite. Drovenik (1980) and Grafenauer (1966) did not found polybasite and acanthite yet; therefore Drovenik supposed that silver (and bismuth) is a component of the galenite and chalcopyrite structure. Indirectly, he made a hint that inadequate analytical method could be the reason for high content of silver in galenite.
The main gangue minerals in the ore are quartz, iron dolomite and subordinately calcite and arago-nite. Particularly variegated are secondary minerals, which crystalized in the oxidizing zone of the Rem{nik mine. Among numerous types only some are stated: cuprite, tenorite, hematite, goethite, manganese oxides and hydroxides, malachite, azurite, smithsonite, cerussite, hydrozincite, brianyoungite, rosasite, au-richalcite, barite, gypsum, linarite, langite, baverite,
posnjakite and carbonate cyanotrichite, aragonite, pyromorphite and chrysocolla.
žorž and co-workers (2007) presented some more frequent minerals (particularly quartz crystals) of the Kobansko area.
Materials and methods of investigation
Presented results are based on field observations and laboratory investigations. Samples were taken near the vein with ore mineralization from the Janiček pit. Diversity of secondary minerals occurring in fractures can be seen under binocular lens, but they are too small for determination. The quantity of gathered samples was not suitable for making either thin sections and/or polished samples; thin coatings would be lost in preparation. A small piece of sample with microcrystallized coating was scanned by X-ray diffractometer. It was equally impossible to isolate thin crystals for chemical analysis. Finally, from the pallet of investigation methods, the only one that remained was scanning electron microscopy (SEM). The analyses were made with SEM JEOL JSM 6490LV at the acceleration energy of 20 kV and at working distance of 10 mm. The BSE mode in low vacuum was used, without coating. Basic semiquantitative chemical composition was determined by Oxford INCA EDS (compo mode) with the same acceleration energy.
Results and discussion
On the 1:100 000 scale Basic geological map of Slovenia, sheet Slovenj Gradec (Mioc & žnidarčič, 1977) the Remšnik mine is marked between the Remšnik nappe composed of Magdalensberg formation rocks and the footwall Pohorje formation of retrograde schists of the Austroalpine basement. A thin belt of phyllites occurs between the two. Determination of phyllites in this area and further eastward is somewhat disputable. Due to multiple secondary alterations, it is not clear whether this layer belongs to real phyllite or to mylonite, originating retrogressively from dyna-mometamorphosed rocks of the Pohorje formation (named Kobansko series after MioC, 1978). It is clear, however, that a part of the Magdalensberg formation rocks, trapped in the thrust zone, is comprised in the phyllite belt.
Macro- and microstructures of the rocks reveal several phases of tectonic activity, including twice reactivated subhorizontal shear movements, due to which dynamometamorphic imprint can be followed in all rocks. The first one is reflected as ductile deformations, yielding mylonitization and foliation. The second shear produced a slaty cleavage, which broadly follows foliation. The origin of these two structures is associated with upper Cretaceous nappe stacking and Tertiary Aus-
troalpine eastward escape (e.g. Fodor et al. 1998, 2002, 2008). Structural parameters of the wider area suggest that Pohorje and Kobansko/Kozjak were still one common block at the time of the Pohorje granodiorite magma emplacement in Lower Miocene and were separated later.
The state of previous investigations does not allow strict definition of the Remšnik ore deposit genesis. Nevertheless, some important relations can be drawn, which neglect its Palaeozoic origin: sulphide mineralization and strong silicification, which obscured structural properties of the rocks, followed cleavage, which is of Tertiary (probably of Miocene) origin; the Kobansko block separated from the Pohorje block probably in middle Miocene and Kobansko was until then, closer to the impact area of the granodiorite intrusion; mineral composition and sulphur isotope composition of the Remšnik and Okoška gora (Pohorje) ore deposits are closely related (Drovenik et al. 1976, 1980). Consequently, there is a great probability that the Remšnik ore mineralization is connected to the Miocene Pohorje magmatism, as has already been proposed by Tornquist (1929), Duhovnik (1956), Berce (1963) and Grafenauer (1965). The question is, whether the mineralization could be related to remobilization of preexisting (Cretaceous/Palaeozoic?) ore minerals, as Drovenik and co-workers (1980) attribute Palaeozoic age to the Okoška gora ore deposit. They argue the age with blastic growth of ore minerals in the time of regional metamorphism, what to us is not a sufficient proof.
Younger oblique fractures, which cut foliation and slaty cleavage, developed as a consequence of renewed shearing. Secondary cleavage plains formed indicating dextral sense of shear (Fig. 3). These fractures are not silicified and contain no primary (sulphide) ore mineralization. All structures are cut by the youngest subvertical faults (Fig. 4) of prevailingly southwest-northeast trend, and subordinately transversely to this direction.
Conditions in the Janiček pit, in which the rocks of the Magdalensberg and Pohorje formations are comprised, show that mostly carbonate lenses and partly wider thrust zone contain ore mineralization. The primary ore mineralization and silicification followed fracture porosity of the older slaty cleavage, which macroscopically follows foliation, while only secondary mineralization can be found in two generations of transverse fractures and faults (Fig. 5). Silicified brecciated rocks appear massive.
Z. Žorž found most of rare secondary minerals in the Remšnik mine and determined them together with Moser (Žorž & Moser, 2002). Among them, particularly interesting is beaverite, the lead-copper-iron-aluminium sulphate. Upon attainable data, beaverite was known only as yellow coatings before the Z. Žorž find; here, caramel
brown, transparent to translucent crystals up to one millimetre in size occur as coatings on quartz (Fig. 6).
Among carbonates, the rosasite and aragonite at partly limonitized quartz base (Fig. 7) are particularly beautiful.
In the base of some secondary minerals, hemi-morphite has been determined by SEM. It is nearly amorphous; therefore, also under SEM, just its colloidal texture is noticed. It can be seen near the ramsbeckite crystals at the left side of Figure 8. The main chemical components of hemimorphite Zn, Si and O are shown at the EDS spectrum (Fig. 8, right).
Rare minerals, determined in the Remšnik mine, occur in traces in microscopic to submicro-scopic sizes; therefore, they have remained unnoticed until recent years. Among them are two especially beautiful forms of sulphates, found in Slovenia for the first time. They belong to secondary minerals formed in the process of near-surface weathering of copper and zinc ores, dumps and slags. The first one belongs to ramsbeckite, which was shortly introduced by Žorž and Trajangva (2010). It represents grassy green to bluish green microcrystal coatings in some fractures and fissures (Fig. 5, lower half).
Determination of the second mineral is still questionable. It occurs in so insignificant a quantity and as so tiny crystals that it is invisible under binocular lens and we did not manage to actually prove its type by SEM analysis. Semiquantitative chemical composition and crystal habit indicate that it most probably belongs to namuwite.
Ramsbeckite
Characteristic Remšnik mine ore veins are composed mostly of chalcopyrite, galenite and sphalerite in the matrix of quartz and carbonates, of which the most frequent is dolomite. In the abandoned pits, the veins reach an average thickness between 3 and 5 centimetres. Thicker veins usually consist of several layers separated by bands of quartz and iron dolomite. The latter looks like split wall rock and/or remobilized carbonate from it. Secondary mineralization is found in opened fractures and faults. Fractures of secondary cleavage cut the ore veins obliquely. Only coatings of secondary minerals characteristic for oxidation zone occur in the youngest steep fractures and faults.
A thicker ore vein with ramsbeckite was found in the lower (second) level, lying about 7 m below the surface. The vein consisted mostly of chalco-pyrite, galenite and sphalerite. Between separate layers of the vein, pyrite crystallized as pentagon dodecahedrons up to 1 mm in size. Coatings of the
copper and zinc secondary minerals occur in the fracture in the upper part of the vein. The fracture in the middle of the vein contained mostly linarite and langite. In the lower part of the vein, malachite and rosasite prevailed in association with some aurichalcite and hydrozincite.
Ramsbeckite is still considered as a rare sulphate despite increasing number of finds. In the Nickel-Strunz classification of minerals, it belongs to the group of sulphates with additional anions, with H20, and to the space group P 21/a 2/m. It is named after Ramsbeck in Germany (Bastenberg mine), where it was found for the first time in 1984 and approved by IMA in 1985 (Internet 2). First description is of Rodenberg and co-workers (1985), who presented ramsbeckite stoichiometric chemical formula (Cu, Zn)7(SO4)2(OH)10^5(H2O) and determined mineral paragenesis, which is comparable with the one in Remšnik mine. Effenberger (1988) determined crystal structure of ramsbeckite. He revised chemical formula, and from previous form it was corrected to (Cu,Zn)15(SO4)4(OH)22^6(H2O).
Ramsbeckite from the Janiček pit occurs in euhedral crystals some tenth of mm in size, maximum up to 0.6 mm and is macroscopically seen only as coloured coatings (Fig. 9). At magnified photo unclear, bright green grains are seen locally (Fig. 10). They have green colour under binocular lense and strong reflection from crystal planes, which prevents us to make a successful photo. Therefore, the photo of ramsbeckite from Penrhiw mine in Wales (Internet 2 or 3) is suitable to better imagine the colour of the mineral, which is the same as the one in Remšnik. The crystals are transparent with silky glassy lustre.
The ramsbeckite crystals of the sample kept in a dry room become slightly less green and blue tint became stronger.
Ramsbeckite crystallize in the monoclinic system. The crystals have diverse habits. The most pronounced is the crystal face of basal pinacoid (001), along which indistinct cleavage can be seen. Distinctive are faces (100) and (010). The face (210) is usually smaller than the others (Fig. 11), while the faces (120) and (310) in most cases are not developed at all (Fig. 12 in the middle). In some crystals only faces (100), (001) and (010) developed (Fig. 12, bottom left and top right).
Sketch of idealized ramsbeckite crystals found so far in the Remšnik mine, is given in Fig. 13. Figure 13 B show indexed crystal faces of forms 1, 2 and 3 shown in figure 13A. Crystal faces defining ramsbeckite morphology are pinacoids (001), (100), (010) and (210) and prism of the 3rd order (110) (Fig. 13, forms 2A, 2B). The prism (110) can be more, or less pronounced. Some of the crystals developed only crystal faces of pinacoids (Fig. 13, sketch 1A, 1B). The most frequent is form 2,
which can have shorter (010) face on the account of longer (210) face, as can be seen in Fig. 13A, form 2. Faces richest, but infrequent is form 3. In this case, an additional face (120) developed on the account of the face (110). Seemingly, face (310) developed on the account of the face (010) (Fig. 13, forms 3A and 3B). An example of such form can be seen in figure 11 at the bottom right half of the biggest crystal in the central intergrown crystal cluster.
Peacor et al. (1987) and Ohnishi et al. (2004) determined ramsbeckite cleavage along basal pi-nacoid, which can be traced also in our case (Fig. 11, crystal at the top of the central intergrown crystals). High crystal of form 4 (Fig. 13A) most probably belongs to twins. As we can find in the Handbook of Mineralogy, version 1 (Bideaux & Nichols, 2004, © 2004-2013), ramsbeckite has repeated twinning, forming cylindrical aggregates. An example of such twin can be seen in SEM image (Fig. 14 left). Similarity of some crystal forms with the ones from Remšnik (e.g. form 1 in Fig. 13A and 13 B) can be seen in figure 1 of Ohnishi and co-workers (2004) from the Hirao mine, near Osaka in Japan, where rhombohedra-like crystals prevail.
Qualitative chemical composition of ramsbeckite is shown in EDS spectrum (Fig. 14 right). Indistinct Si peak occurs due to small grains on the crystal surface. Unusually high crystal form for tabular ramsbeckite is the same as form 4 in figure 13A.
An EDS spectrum of pure ramsbeckite (Fig. 15) is scanned on the clear smooth surface of the bottom crystal at the right edge of figure 11. Therefore, no admixtures of Si appear in the spectrum in comparison to Fig. 14.
Several rare sulphate minerals are related to ramsbeckite in chemical composition as for example: langite, posnjakite, wroewolfeite, spangolite, ktenasite, and also namuwite.
An attempt was made to scan a piece of sample with microcrystalline coating with X-ray diffrac-tometer, but the analysis was not successful.
Namuwite
Beside ramsbeckite another microcrystalline secondary sulphate is present in the composition of macroscopically amorphous bluish green coatings. With a shade of doubt, it is determined as namuwite.
Namuwite was described for the first time by Bevins and co-workers in 1982. It was determined in a sample originating from the Aberllyn mine. It is kept in the National Museum of Wales, whereupon its name originates (NA-MU-W-ite). The same year, the mineral was approved by IMA (Internet 4). It was shortly presented in the American
mineralogists periodical under the »New mineral names« (Fleischer & Pabst, 1983). From then on, the mineral was found in oxidation zones of Cu, Zn ore deposits, as well as in mine gouges in several places around the world.
Namuwite chemical formula is (Cu, Zn)4(SO4) (OH)6-4(H2O) (Bevins et al., 1982). The authors described it as a sea blue mineral with emerald luster. Because only chemical composition, determined by SEM EDS, had been considered in the initial investigations, it was ascribed to ramsbeck-ite (žorž & Trajanova, 2010). Due to its hexagonal form the determination was dubious; therefore we made additional SEM analyses. The x-ray diffraction analysis was made together with ramsbeck-ite, but was unsuccessful. EDS qualitative chemical composition of namuwite is the same as the one of ramsbeckite. It differs semiquantitatively, but because of small grains and the use of unpolished sample the results were not reliable and are not applicable.
As for the form of rosettes namuwite is similar to another sulphate mineral, posnjakite. They can be differentiated according to the colour (posn-jakite is blue, namuwite pale green) and chemical composition (Zn beside Cu in namuwite). Based on the mentioned facts and on crystal form, we concluded that the mineral most probably belongs to namuwite. Typical are light green submicroscopic flowery aggregates (Fig. 16) on crusty coatings of related chemical composition, occurring together with ramsbeckite. They are the same as the forms described by Bevins and co-workers (1982) and Groat (1996). According to their data namuwite is isomorphous with the synthetic zinc sulphate (Zn4SO4OH)2-4H2O).
The namuwite crystals grow out of predominantly amorphous ground and rarely exceed 50 pm, exceptionally 80 pm in size. They have pronounced cleavage along basal pinacoid (001). Frequent transverse intergrowing of leaflets can be seen, like the ones in figures 16 (near the left edge) and 17.
Qualitative chemical composition of the Remšnik mine namuwite from figure 17 is shown in figure 18. Like ramsbeckite, it belongs to copper, zinc sulphate with additional anions and H2O. The spectra peaks have disproportional heights due to the unfavourable orientation of the crystal surface according to the detector position.
Groat (1996) determined crystal structure of namuwite. It consists of repeated tetrahedral-octahedral-tetrahedral (T - O - T) layers held together by hydrogen bonds to interstitial H2O molecules. The author found out that namuwite is subjected to hydration, dehydration processes, and to transitions from tetrahydrate to pentahy-drate at about room temperature.
Conclusion
Polymetallic ore mineralization of the Remšnik mine developed along cleavage fractures coinciding with foliation, which indicates its Tertiary age and most probable connection with the Pohorje magmatism. Numerous secondary minerals crystallized in younger fractures in the process of oxidation and near-surface weathering. Among them some very rare types can be found, such as copper zinc sulphates ramsbeckite and namuwite (?) described for the first time in Slovenia. The namu-wite determination is still not univocal; therefore, we hope that the next find will be of bigger quantity enabling thus the use of analytical techniques which will confirm or reject the present determination.
Acknowledgement
The investigations were financially supported by the Slovenian Research Agency within the frame of the research programme P1-0025, Sedimentology and mineral resources. We thank to reviewers for helpful comments and corrections and to Dr Miloš Miller for his assistance at the SEM.
Literatura - References
Arhiv RS, 1950: Rudarska knjiga A za okrožje Celje. Ljubljana: 185-204.
Arhiv RS, 1850a: Fevdna in koncesijska knjiga: Drauwalder Gesmbh Lehensbrief.
Berce, B. 1963: The formation of the ore-deposits in Slovenia. Rendiconti della Societa Mineral-ogica Italiana, 19: 1-16.
Bevins, R.E., Turgoose, S. & Williams, P.A. 1982: Namuwite, (Zn, Cu)4SO4(OH)6 • 4H2O, a new mineral from Wales. Mineralogical Magazine, 46: 51-54.
Bideaux, a. & Nichols, B. 2004: Handbook of mineralogy. Mineralogical Soc. of America. Mineral Data Publishing, version 1/ V: © 2004-2013, 791 p.
Drovenik, M., Duhovnik, J., & Pezdi~, J. 1976: Izotopska sestava žvepla v sulfidnih rudnih nahajališčih v Sloveniji. Rud. met. zbornik, 2-3: 193-246.
Drovenik, M., Pleni~ar, M. & Drovenik, F. 1980: Nastanek rudišč v SR Sloveniji. Geologija, 23/1: 1-157.
Duhovnik, J. 1956: Über die metallogenetischen Epochen und Provinzen Jugoslawiens. Berg-und Hüttenmännische Monatshefte 101. Jahrgang 2:30-32.
Effenberger, H. 1988: Ramsbeckite, (Cu, Zn)15(OH)22(SO4)4 • 6H2O: revision of the chemical formula based on a structure determination. Neues Jahrbuch für Mineralogie, Monatshefte, 38-48.
Fleischer, M. & Pabst, A. 1983: New mineral names. American Mineralogist 68: 280-283.
Fodor, L., Gerdes, A., Dunkl, I., Koroknai, B., Pecskay, Z., Trajanova, M., Horväth, P., vrabec, M., Jelen, B., Balogh, K. & Frisch, W. 2008: Miocene emplacement and rapid cooling of the Pohorje pluton at the Alpine-Pannonian-Dinaridic junction, Slovenia. Swiss J. Geosci., Birkhäuser Verlag, 255-271.
Fodor, L., Jelen, B., Märton, E., Rifelj, H., Kraljic, M., Kevric, R., Märton, P., Koroknai, B. & Bäldi-Beke, M. 2002: Miocene to Quaternary deformation, stratigraphy and paleogeography in Northeastern Slovenia and Southwestern Hungary. Geologija, 45/1: 103-114, Ljubljana; doi:10.5474/geologija.2002.009.
Fodor, L., Jelen, B., Märton, E., Skaberne, D., Čar, J. & vrabec, M. 1998: Miocene - Pliocene tectonic evolution of the Slovenian Periadriatic fault: implications for Alpine - Carpathian extrusion models. Tectonics, 17: 690-709.
Geološka služba rudnika Mežica I. 1984-1989: Metalogenetska problematika kovinskih nahajališč v metamorfnih kameninah na Kobanskem in Pohorju, ECM Inštitut za gospodarski in socialni razvoj Ravne na Kor. Arhivska poročila o delu od 1984 do 1989.
Groat, L.A. 1996: The crystal structure of namuwite, a mineral with Zn in tetrahedral and octahedral coordination, and its relationship to the synthetic basic zinc sulfates. American mineralogist, 81/1-2: 238-243.
Grafenauer, S. 1965: Genetska razčlenitev svinčevih in cinkovih nahajališč v Sloveniji. Rud. Met. Zbornik, 2: 165-171.
Grafenauer, S. 1966: Metalogenija i mineraloške karakteristike bakrovih pojava u Sloveniji. Referati VI. savetovanja geologa SFRJ II, Ohrid, 377-396.
Hegemann, F. 1960: Über extrusiv-sedimentäre Erzlagerstätten der Ostalpen. II. Teil. Zeitschrift für Erzbergbau und Metallhüttenwesen, B.-A. XII: 122-127.
Hodenberg, R.v. Krause, W., Schnorrer-Köhler, G. & Täuber, H. 1985: Ramsbeckite, (Cu, Zn)7(SO4)2(OH)10 • 5H2O, a new mineral. Neues Jahrbuch für Mineralogie, Monatshefte: 550556.
Mason, J.S. & Green, D. I. 1995: Supergene minerals including exceptional ramsbeckite from Penhriw mine, Ystumtuen, Dyfed. UK Journal of Mines and Minerals, 15: 21-27.
Mio~, P.& Ramovš A. 1973: Erster Nachweis des Unterdevons im Kozjak Gebirge (Posruck), westlich von Maribor (Zentralalpen). Bull. Sci. Cons., Acad. Sci. Yugosl. (A), 18/7-9: 135136.
Mio~, P. 1978: Osnovna geološka karta SFRJ 1 : 100.000. Tolmač za list Slovenj Gradec. Zvezni geološki zavod, Beograd: 74 p.
Mioč, P. & Žnidarčič, m. 1977: Osnovna geolo{ka karta SFRJ 1 : 100.000, list Slovenj Gradec. Zv. geol. zavod, Beograd. ohnishi, m., Kobayashi, 8., Kusachi, i., Yamakawa, J. & shirakami, m. 2004: Ramsbeckite from the Hirao mine at Minoo, Osaka, Japan. Journal of Mineral. and Petrol. Sci., 99: 19-24. orlandi, p. & PercHiAzzi, N. 1989: Ramsbeckite, (Cu, Zn)15(OH)22(SO4)4 ■ 6H2O, a first occurrence for Italy from "La Veneziana" mine, Valle dei Mercanti, Vicenza. Eur. Journ. Mineral., 1: 147149.
Peacor, D.R., Dunn, P.J. & sturman, B.D. 1987: Ramsbeckite: an American occurrence at the Ecton mine, Pennsylvania. Mineralog. Record, 18:131-132.
Štrucl, i. 1984-1989: Metalogenetska problematika kovinskih nahajali{č v metamorfnih kameninah na Kobanskem in Pohorju, ECM In{titut za gospodarski in socialni razvoj Ravne na Kor. Arhivska poročila o delu od 1984 do 1989.
Tornquist, a. 1929: Die perimagmatische BleiKupfer-Silber-Zinkerzlagerstätte von Offberg im Remschnigg. Akad. Wissenschaften, mat.-naturw. Kl. Abt. I, 138 /1-2: 47-68. Žorž, Z. & Moser , B. 2002: Remšnik, zgodovina-geologija-minerali. Založba Voranc, Ravne na Koro{kem.
Žorž, Z., Golob, F., Rečnik, A. & Hinterlech-ner-Ravnik, a. 2007: Mineralizirane alpske razpoke na Kobanskem in na severnem Pohorju. V: Rečnik, A. (ur.): Nahajališča mineralov v Sloveniji. Institut Jožef Stefan, Odsek za na-nostrukt. materiale: 269-272.
Internetni viri dostopni / Internet resources available to 20.5.2013 Internet 1: http://www.mindat.org/min-3358.html Internet 2: http://www.museumwales.ac.uk/en/
800/?mineral=120 Internet 3: http://webmineral.com/specimens/pic
show.php?id=966&target=Ramsbeckite Internet 4: http://www.mindat.org/min-2837.html