Yellowish crystals of the rare manganese sulphate mineral ilesite in a matrix of white apjohnite from one of the few localities known worldwide for ilesite. From: Santa Ana Mine, Mazarron, Murcia, Spain. — Photo: David Hospital · CC BY-SA 4.0
Ilesite
Ilesite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Mn²⁺(SO₄)·4H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/n). It is a member of the Starkeyite structural group.
Key properties: Mohs hardness 2–3; specific gravity 2.26; optically biaxial.
IMA symbol Ile, grandfathered status — known before the IMA’s founding, named in 1881.
A rare secondary mineral found in the oxidized zones of sulfide deposits.
It is found associated with Pyrite, sphalerite, galena (McDonnell claim, Colorado, USA); rozenite, epsomite, copiapite, gypsum, melanterite, chvaleticeite (Chvaletice, Czech Republic).
The mineral was named to honor Malvern Wells Iles (1852–1890), American metallurgist of Denver, Colorado, USA, who made the first chemical analysis of the species.