(Micromount) Uraninite - Shaft #3, Příbram, Czech Republic

Uraninite from Příbram, Czech Republic, is a striking example of botryoidal uranium oxide (UO₂), also known as pitchblende, formed in hydrothermal vein systems within the Bohemian Massif. Its lustrous, steel-black to brownish-black globular aggregates exhibit a submetallic to greasy luster and display a dense, conchoidal- to uneven-fracture structure. Chemically, it often contains significant secondary lead (PbO), calcium, and silica, reflecting partial oxidation and alteration processes that lead to the formation of gummite species in weathered zones . In Příbram, uraninite occurs closely associated with calcite, barite, and sulfide veins like galena and sphalerite, forming in a late-stage carbonate–uraninite phase within deeply tectonized Proterozoic and Cambrian host rocks .

The Příbram district, especially the Bytíz mine, was one of Europe’s most prolific uranium producers, accounting for over half of Czechoslovakia’s uranium output between 1950 and 1991—totaling some 50 200 t U  This rich deposit spanned a 25 km length and mined depths exceeding 1 500 m, with uraninite typically occurring as veinlets, crusts, and pods in calcite gangue along fault zones. Collectors and researchers prize these specimens for their attractive botryoidal habit and metallic sheen. Enthusiasts on forums like r/Radioactive_Rocks often note their rarity, beauty, and radioactive intensity, praising pieces from Příbram for their classic vein textures and geological significance.

Approx. specimen size: 15mm x 10mm x 5mm

Approx. specimen weight: 1.26 grams

Approx. specimen activity on an SE International Ranger EXP: 9000 cpm