Images
Formula: (H5O2)Fe3+(SO4)2.2H2O
Hydrated normal sulphate
Crystal System: Orthorhombic
Specific gravity: 2.23 measured, 2.21 calculated
Hardness: 2
Streak: White
Colour: Blue, colourless, white, yellow, light green, grey, colourless in transmitted light
Solubility: Slowly soluble in water, easily soluble in acids
Common impurities: As
Environments
Rhomboclase is an uncommon secondary mineral formed by
alteration of pyrite, marcasite or
pyrrhotite, especially in an arid climate; it is typically of post-mining
origin. Associated minerals include szomolnokite,
copiapite, römerite,
voltaite, epsomite,
halotrichite, melanterite,
chalcanthite and pyrite
(HOM, Mindat).
Localities
At the Socavon mine, Oruro City, Cercado Province, Oruro, Bolivia, rhomboclase occurs as thin platy crystals up
to 2 cm in size with melanterite and
copiapite
(Dana).
At the Alcaparrosa Mine, Sierra Gorda, Antofagasta Province, Antofagasta, Chile, colourless and faintly brownish-purple
rhomboclase and intimately associated szomolnokite and
römerite with bright angular pieces of
pyrite scattered through the minerals
(AM 23.669-760).
At the type locality, Smolník, Gelnica District, Košice Region, Slovakia, rhomboclase occurs in an altering
pyritic ore body, associated with
szomolnokite and
copiapite
(Mindat).
Back to Minerals