Bismutite altering from Bismuth

specimen number:
2133222

location:
San Andres Mts., New Mexico, USA

description:
Masses of native bismuth in the process of being replaced by earthy bismutite. The specimen comes with an old label from Colorado dealer Robert Roots.

Bismutite is a secondary bismuth carbonate mineral that typically forms as an oxidation product of primary bismuth minerals such as bismuthinite or native bismuth. Geologically, it is most frequently found in the weathered zones of hydrothermal ore veins and granitic pegmatites, where it occurs as a result of the chemical alteration of bismuth-bearing sulfides in the presence of carbon dioxide. The mineral usually lacks a well-defined crystal structure, appearing instead as earthy, massive, or fibrous crusts and powdery coatings. Its color ranges from a dull straw-yellow and yellowish-gray to a pale green or even brown, often possessing a high specific gravity that is characteristic of bismuth-based compounds.

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