Gummite


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gummite

[′gə‚mīt]
(mineralogy)
Any of various yellow, orange, red, or brown secondary minerals containing hydrous oxides of uranium, thorium, and lead. Also known as uranium ocher.

Gummite

 

mineral formations of unstable composition that comprise mixtures of cryptocrystalline aggregates consisting of hydrated oxides and some uranium hydrosilicates. The principal minerals that form gummite are clarkeite (Na, K)22r(Ca. Pb)rU2O7.y H2O, fourmarierite PbO-4UO3-7—8H20, and kasolite Pb(U02)[Si04]H20; they are rarely found in pure form. Gummite forms thin crusts and irregular or circular concretions with a conchoidal fracture and a light-yellow or red-orange resinous luster. Its hardness on the mineralogical scale is 2.5–3 and its density. 4,700–5,800 kg/m3. Gummite is brittle. It develops as a result of changes in uraninite or pitchblende in the zone of oxidation of primary uranium ores.

G. P. BARSANOV