A grouping of large thick glassy mostly gemmy quartz crystals, these hosting pale yellow rhombohedral crystals of calcite. This is in terrific condition. The inner cores of these crystals are a purple amethyst in color as seen in the video.The Borieva Mine, located within the Madan ore field of the Rhodope Mountains in southern Bulgaria, is part of a historic mining district with roots dating back to ancient Thracian and Roman times. Geologically, the deposit is situated in a metamorphic core complex where Paleogene extensional magmatism drove hydrothermal activity. Hot, metal-bearing fluids circulated through tectonic structures and deposited rich polymetallic ores primarily as vein and replacement bodies hosted in crystalline marbles and gneisses. Modern industrial extraction developed significantly during the twentieth century to supply lead and zinc. Today, the underground workings of the Borieva Mine are world-famous among mineral collectors for yielding exceptionally aesthetic and well-crystallized specimens of galena, sphalerite, pyrite, chalcopyrite, quartz, and calcite.
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