Ángelaite
Ángelaite is a rare sulfosalt mineral with the chemical formula copper(II) silver lead bismuth tetrasulfide. It crystallizes in the orthorhombic system and is classified under the Strunz classification as 2.JB.25f. This mineral is typically metallic in luster and exhibits a dark gray to black color. Its physical properties include a hardness of approximately 2.5 to 3 on the Mohs scale and a relatively high density. Ángelaite is notable for its complex chemical composition, combining multiple heavy metals with sulfur, and is considered a member of the sulfosalt mineral group.
Composition
- BiBismuth26.8%
- PbLead26.6%
- SSulfur16.5%
- CuCopper16.3%
- AgSilver13.8%
Overview
Ángelaite is a rare sulfosalt mineral with the chemical formula copper(II) silver lead bismuth tetrasulfide. It crystallizes in the orthorhombic system and is classified under the Strunz classification as 2.JB.25f. This mineral is typically metallic in luster and exhibits a dark gray to black color. Its physical properties include a hardness of approximately 2.5 to 3 on the Mohs scale and a relatively high density. Ángelaite is notable for its complex chemical composition, combining multiple heavy metals with sulfur, and is considered a member of the sulfosalt mineral group.
Etymology
Ángelaite is named after the naming locality, which is the place where the mineral was first identified. The mineral was later renamed by the IMA, indicating a change in its official designation.
How to recognize it
Ángelaite can be identified by its metallic luster, dark gray to black color, and relatively low hardness of 2.5 to 3 on the Mohs scale. It can be distinguished from other similar sulfosalt minerals by its unique chemical composition, which includes copper, silver, lead, and bismuth. A streak test may reveal a dark gray to black streak, and its high density can be a helpful diagnostic feature. It is often confused with other dark sulfide minerals but can be differentiated through chemical analysis.
Trivia
Ángelaite is notable for its complex chemical formula, which includes four different metal elements combined with sulfur. It is a rare mineral, and its classification under the sulfosalt group highlights its unique chemical structure. Additionally, its renaming by the IMA indicates that it may have been previously misclassified or had an earlier name that was later revised.