| Rhomboclase | |
|---|---|
| General | |
| Category | Sulfate mineral |
| Formula (repeating unit) | H5Fe3+O2(SO4)2·2(H2O) |
| IMA symbol | Rbc[1] |
| Strunz classification | 7.CB.55 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pnma |
| Identification | |
| Color | blue, colourless, white, yellow, light green, grey |
| Luster | sub-Vitreous, Pearly |
| Streak | white |
| Diaphaneity | transparent |
| References | [2][3] |
Rhomboclase is an acidic iron sulfate mineral with a formula reported as H5Fe3+O2(SO4)2·2(H2O)[4] or HFe(SO4)2·4(H2O).[2] It crystallizes in the orthorhombic system and typically occurs as tabular crystals with a rhombic outline.[4] It occurs as transparent colorless, blue, green, yellow or grey crystals with a vitreous to pearly luster.[3]
Rhomboclase forms within the oxidizing environment of pyrite rich ore deposits and is reported as a post mine mineral of arid regions.[4]
It was first described in 1888 for an occurrence in Slovakia and was named from Latin, rhombus, rhomb, and Greek klasis, to break, for its crystal form and perfect basal cleavage.[2]