The brown yakhontovite PS is ~ 1½ mm in diameter. Yakhontovite PS after tennantite. The back of the specimen has clinotyrolite. From: La Amorosa mine, San Rafael claim, Villahermosa del Rio, Castellón, Valencian Community, Spain — Photo: Modris Baum · CC0
Yakhontovite
Yakhontovite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Ca,Na,K)₀.₂(Cu,Fe,Mg)₂Si₄O₁₀(OH)₂·3H₂O.
It crystallizes in the monoclinic crystal system. It is a member of the Clay, Smectite-vermiculite structural group.
Key properties: Mohs hardness 2–3; Dull luster; optically biaxial.
IMA symbol Ykh, IMA status: approved, named in 1984.
Occurs as veins and coatings in deeply oxidized sulfide-cassiterite ores.
It is found associated with Pyrrhotite, chalcopyrite, pyrite, stannite, malachite, pseudomalachite, chrysocolla, iron oxides, quartz.
The name refers to Liya Konstantinova Yakhontova (1925{), Russian mineralogist, Moscow Univesity, Moscow, Russia.