Dark brown almost black crystal aggregates of the extremely rare chromium mineral rilandite from the type and only known locality worldwide, the Riland mine in Colorado (Riland Uranium Claim, Meeker, Rio Blanco County, Colorado, United States of America). Ex.Vandenbroucke collection. — Photo: David Hospital · CC BY-SA 4.0
Rilandite
Rilandite is an IMA-recognized mineral species in the silicate class, with the chemical formula Cr₆SiO₁₁·5H₂O.
Key properties: Mohs hardness 2–3; Grayish brown streak; Brilliant on fresh surface, otherwise dull, pitchy luster.
IMA symbol Ril, IMA status: questionable, named in 1933.
On the outer surface and in shallow recesses of a petrified log in sandstone.
It is found associated with Carnotite, organic matter.
The name refers to James L. Riland, newspaper publisher from Meeker, Colorado, USA, owner of the mining claims on which the mineral was discovered.