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Uraninite Altering to Gummite


Gummite is not a definitive mineral species, but rather an unspecific mixture of secondary uranium minerals, especially Becquerelite, Boltwoodite, Clarkeite, Curite, Fourmarierite, Kasolite, Soddyite, and Uranophane. It lacks a definitive chemical formula and crystal structure, though it is still listed as a mineral in many mineral guides.

Gummite forms from the oxidation of Uraninite and is present in most uranium deposits. It often forms as a partial alteration of Uraninite, where the inner core remains dull-colored Uraninite, and the outer layers as brightly colored Gummite. The origination of the name Gummite is unknown, but it is presumably named for its rubber or gum-like consistency. Gummite is a radioactive mineral, and should be stored with all the precautions exercised with radioactive minerals.
Chemical Formula Lacks definitive chemical formula
Composition Mainly uranium oxides
Color Red, orange, yellow, and brown; often multicolored in splotchy patches
Streak Light yellow to light orange
Hardness 2.5 - 5
Crystal System Amorphous
Crystal Forms
and Aggregates
Most often massive and as encrusting. Also in rounded and grainy masses and compact form, as well as in embedded dendritic formations.
Transparency Slightly translucent to opaque
Specific Gravity 3.9 - 6.4
Luster Resinous, Waxy, dull
Cleavage None
Fracture Uneven
Tenacity Brittle
Other ID Marks Gummite is radioactive.
In Group Oxides; Simple Oxides
Striking Features Radioactivity and formation in uranium deposits, color
Environment In granite pegmatite veins and in hydrothermal replacement deposits.
Rock Type Igneous, Metamorphic
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 2


 -  Brown formation of Gummite from Spruce Pine, North Carolina, that forms between yellow Gummite and black Uraninite.
 -  Describing Gummite with an unaltered Uraninite core.
 -  Gummite from the Elias mine, Jáchymov, Czech Republic.
 -  Yttrium-rich variety of Gummite.

Gummite is an ore of uranium in uranium deposits. Mineral specimens are sometimes sliced and polished to show embedded color patterns of Gummite within the matrix.

The most important locality for this mineral is the Ruggles Mine, Grafton, New Hampshire, where the Gummite is found in yellow masses associated with altering Uraninite and in association with dendritic Uraninite. Other localities that have produced specimens in collections include Spruce Pine, Mitchell Co., North Carolina; and the Luiswishi Mine, Lubumbashi, Katanga Copper Belt, Democratic Republic of Congo; and Jáchymov, in the Karlovy Vary region of Bohemia, Czech Republic.

Uraninite (var. Pitchblende), Albite, Microcline, Uranophane, Zircon, Muscovite


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