SPHALERITE WITH DOLOMITE & QUARTZ

ABOUT THE SPECIMEN

Tetrahedral crystals of black sphalerite arranged in complex groupings, with a “frosting” of cream colored dolomite dotted in between and around the edges of many crystals. Quartz crystals and lustrous galena cubes are also visible around the sides and back of the specimen. Though not an uncommon association from Madan, this one here is particularly nice for the composition between the light and dark minerals, as well as the sharpness of the crystals when viewed up close.

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Krushev Dol ("Valley of the Pears") sits within the Madan Ore Field, part of the Central Rhodopian metamorphic core complex where Pb-Zn mineralization formed approximately 30-29 Ma during post-orogenic extensional collapse. Hydrothermal veins and carbonate replacement bodies developed in high-grade metamorphic gneisses and marbles as large-scale fluid circulation was driven by elevated heat flow during rapid crustal thinning and exhumation. Sphalerite appears in multiple habits: gemmy translucent cleiophane variety in yellow, orange, red, and green colors reaching 2 cm, alongside black opaque tetrahedral forms. Crystals commonly occur with galena, chalcopyrite, quartz, and white calcite, often extracted from depths exceeding 450 meters. What distinguishes Krushev Dol within the Madan district is the frequency of transparent gem-quality sphalerite specimens suitable for faceting. The mine also yielded beryllium mineralization including bertrandite, an unusual association for base metal deposits. Specimens typically show sharp trigonic surface features and excellent metallic to resinous luster. Mining operations have reduced or ceased in recent decades following Bulgaria's economic changes, making quality material from this classic European sulfide locality increasingly difficult to obtain.