Outstanding sharp brown crystal of the rare silicate mineral chayesite. Chayesite has only been found in 5 localities worldwide. From: Sierra de las Cabras, Cancarix, Albacete, Castilla La Mancha, Spain. — Photo: David Hospital · CC BY-SA 4.0
Chayesite
Chayesite is an IMA-recognized mineral species in the silicate class, with the chemical formula KMg₄Fe³⁺[Si₁₂O₃₀].
It crystallizes in the hexagonal crystal system (space group P6/mcc). It is a member of the Milarite structural group.
Key properties: specific gravity 2.68; White streak; Vitreous luster; optically uniaxial.
IMA symbol Cys, IMA status: approved, named in 1987.
A late-crystallizing mineral, nonuniformly distributed in the groundmass of lamproites.
It is found associated with Potassian richterite, diopside, potassic feldspar.
In honor of Dr. Felix Chayes (1916–1993) of the Geophysical Laboratory, Carnegie Institute, Washington, D.C., USA.