Outstanding yellow crystals of the very rare mineral donbassite from the type locality in Donbass (Donetsk) in a contrasting dark matrix. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Donbassite
An aluminium-rich member of the chlorite group named for the Donbas coal region of Ukraine.
Intro adapted from Wikipedia (CC BY-SA).
Donbassite is an IMA-recognized mineral species in the silicate class, with the chemical formula Al₂(Si₃Al)O₁₀(OH)₂·Al₂.₃₃(OH)₆.
It crystallizes in the monoclinic crystal system (space group C2). It is a member of the Chlorite, Clay structural group.
Key properties: Mohs hardness 2.5; specific gravity 2.63; Pearly luster; optically biaxial.
IMA symbol Dbs, grandfathered status — known before the IMA’s founding, named in 1940.
Found in the lode walls and crushed zones in ore veins and as coatings on slickensides of coals. In soils and sediments in very aluminum-rich environments.
The name refers to occurrences in the DONets BASin, Ukraine.