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Epithermal Bicolor Black and White Calcite Spheres from Herja Ore Deposit, Baia Mare Neogene Ore District, Romania-Genetic Considerations

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Babeş-Bolyai University, Faculty of Biology and Geology, Department of Geology, 1, M. Kogălniceanu str., Cluj-Napoca 400084, Romania
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Babeş-Bolyai University, Faculty of Physics, 1, M. Kogălniceanu str., Cluj-Napoca 400084, Romania
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Babeş-Bolyai University, Faculty of European Studies, 1, Em. de Martonne, Cluj-Napoca 400090, Romania
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County Museum of Mineralogy, Bulevardul Traian nr. 8, Baia Mare 430212, Romania
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Technical University of Cluj-Napoca, North University Centre of Baia Mare, 62A, Dr. Victor Babeș str., Baia Mare 430083, Romania
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Author to whom correspondence should be addressed.
Minerals 2019, 9(6), 352; https://doi.org/10.3390/min9060352
Received: 24 April 2019 / Revised: 4 June 2019 / Accepted: 5 June 2019 / Published: 8 June 2019
(This article belongs to the Special Issue Calcite)
White, black, or white and black calcite spheres were discovered during the 20th century within geodes from several Pb-Zn ± Au-Ag epithermal vein deposits from the Baia Mare ore district, Eastern Carpathians, Romania, with the Herja ore deposit being the maiden occurrence. The black or black and white calcite spheres are systematically accompanied by needle-like sulfosalts which are known by the local miners as “plumosite”. The genesis of epithermal spheres composed partly or entirely of black calcite is considered to be related to the deposition of calcite within voids filled by hydrothermal fluids that contain acicular crystals of sulfosalts, mostly jamesonite in suspension. The proposed genetic model involves gravitational concentration of sulfosalt acicular crystals towards the base of open spaces within paleochannels of epithermal fluid flow and the subsequent formation of calcite spheres by geochemical self organization of amorphous calcium carbonate that crystallized to calcite via vaterite. View Full-Text
Keywords: calcite spheres; jamesonite; berthierite; gravitational concentration; Herja; Baia Mare; Romania calcite spheres; jamesonite; berthierite; gravitational concentration; Herja; Baia Mare; Romania
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Mârza, I.; Tămaș, C.G.; Tetean, R.; Andreica, A.; Denuț, I.; Kovács, R. Epithermal Bicolor Black and White Calcite Spheres from Herja Ore Deposit, Baia Mare Neogene Ore District, Romania-Genetic Considerations. Minerals 2019, 9, 352.

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