DESCLOIZITE

ABOUT THE SPECIMEN

Super aesthetic miniature of the rare lead-zinc vanadate mineral descloizite. From the now closed Berg Aukas Mine in the Otavi Mountain region of Namibia, by far the world's best locale for the mineral species. There's an abundance of the beautiful, sharp dendritic blades that are sought after with these pieces, and they all have multiple patches of iridescence. The crystals also have a homoepitaxial growth on top that gives a super sparkly look when in direct light. As far as Berg Aukas pieces go, this is an excellent representation of what makes pieces from this locale so highly prized.

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Berg Aukas is a Zn-Pb-V deposit hosted in Precambrian Otavi dolomite - the same carbonate-dominated Otavi Mountainland terrane as Tsumeb - worked from 1920 to 1978 with ore averaging 16.8% Zn, 4% Pb, and 0.93% vanadium pentoxide. Descloizite formed as the dominant supergene vanadate in the oxidized zone surrounding primary sphalerite-willemite orebodies, precipitating in vug and fracture fill within karst breccias as descending meteoric waters mobilized vanadium and deposited it as a lead-zinc vanadate hydroxide. A peer-reviewed Economic Geology study (2007) dated the principal descloizite formation to 24–33 Ma, tying it to post-Gondwanan erosional episodes and Atlantic rifting phases rather than to primary mineralization. Crystals occur as spearpoint-shaped blades in divergent sprays, deep chocolate-brown with a submetallic to resinous luster, occasionally carrying a secondary calcite or dolomite overgrowth on crystal faces that produces a distinctive two-toned appearance. Berg Aukas is the undisputed world standard for the species - no other locality has approached it for crystal size or quality - and with mining permanently ceased in 1978, available material is limited to what was extracted across its six decades of operation.