Angelaite, also known as angelaite mineral, is a relatively rare copper arsenate mineral. It belongs to the monoclinic crystal system and has a chemical formula of Cu_2Ag_2Pb(AsO_4)(SO_4)(OH,H_2O)_6. The mineral typically occurs in granular or fibrous forms, with a characteristic green color.
Angelaite is named after the locality where it was first discovered, the Angela mine in Ellenville, New York, USA. It is primarily found in oxidized, polymetallic ore deposits associated with copper and lead minerals. The mineral forms in the oxidation zone of these deposits, where sulfide minerals are exposed to weathering processes.
In terms of physical properties, angelaite has a Mohs hardness of 3-3.5, which makes it relatively soft compared to other minerals. It also has a vitreous to pearly luster, and its streak is white. Moreover, angelaite exhibits perfect cleavage along its crystal surfaces, which gives it a distinctively uneven fracture.
From a chemical perspective, angelaite is categorized as an arsenate mineral due to its composition containing arsenate ions (AsO_4^3-). It shares a similar chemical structure with other arsenate minerals, but its unique combination of elements gives it its own distinctiveness.
Angelaite is primarily sought after by mineral collectors due to its rarity and aesthetic appeal. Its vibrant green color, fibrous or granular texture, and association with other minerals can make it a visually appealing addition to a collection. However, its scarcity limits its accessibility in both the collector's market and scientific research.
