| Felsőbányaite | |
| Category: | Sulfate mineral |
| Formula: | Al4(SO4)(OH)10·4H2O |
| Imasymbol: | Fsb[1] |
| Strunz: | 7.DD.05 |
| System: | Monoclinic |
| Class: | Sphenoidal (2) (same H-M symbol) |
| Symmetry: | P21 |
| Unit Cell: | a = 13.026 Å, b = 10.015 Å, c = 11.115 Å; β = 104.34°; Z = 4 |
| Color: | White to pale yellow, pale brown |
| Habit: | Globular masses, minute rhombic crystals |
| Cleavage: | Distinct to good on and |
| Mohs: | 1.5 |
| Luster: | Vitreous, pearly on cleavage surfaces |
| Diaphaneity: | Semitransparent |
| Gravity: | 2.33 |
| Opticalprop: | Biaxial (+) |
| Refractive: | n = 1.515–1.540 |
| References: | [2] [3] |
Felsőbányaite or basaluminite is a hydrated aluminium sulfate mineral with formula: Al4(SO4)(OH)10·4H2O. It is a rare white to pale yellow mineral which typically occurs as globular masses and incrustations or as minute rhombic crystals. It crystallizes in the monoclinic crystal system.[3] [2]
It occurs as a weathering product under acidic conditions associated with pyrite or marcasite decomposition. Associated minerals include hydrobasaluminite, hydroargillite, meta-aluminite, allophane, gibbsite, gypsum and aragonite.[3]
Felsőbányaite was first described in 1853 for an occurrence in the Baia Sprie mine, Baia Sprie (Felsőbánya), Maramureș County, Romania, and named for the locality.[2] The mineral name basaluminite was used for an occurrence of the same mineral in England in 1948 and discredited by the International Mineralogical Association (IMA) in 2006.[4]