Cadmoselite

Cadmoselite is a rare cadmium selenide mineral with chemical formula CdSe. Cadmoselite crystallizes in the hexagonal system and occurs as black to pale grey opaque crystals and grains.^[1][2]

Cadmoselite
Cadmoselite from the type locality: Ust' Uyok Deposit, Turan District, Tuva Republic, Russian Federation
General
Category	Minerals
Formula	CdSe
IMA symbol	Cds
Identification
Formula mass	191.37
Color	Black to pale grey
Luster	Adamantine – Resinous
Streak	Black
Diaphaneity	Translucent to Opaque
Specific gravity	5.47

It was first described in 1957 for an occurrence in Tuva. The mineral occurs as interstitial grains in sandstone formed under reducing alkaline diagenetic conditions.^[1][2]