| Mineral | ALUNITE |
| Chemistry | KAl 3 (SO 4 ) 2 (OH) 6 |
| Class | Sulfates |
| Uses | As a minor source of alum, potassium and aluminum and as mineral specimens. |
| CrystalSystem | Trigonal |
| CrystalHabits | include tabular to flattened rhombohedral looking crystals.The rhombohedrons are actually a combination of two trigonal pyramids.Crystals are somewhat scarce, small and usually line the fissures in alunite rocks, more commonly as earthy masses, films or crusts, botryoidal and granular. |
| Fracture | fair in one direction (basal), but only seen in the larger crystals. |
| Hardness | 3½ - 4 |
| Characteristics | Some specimens fluoresce a nice orange color under longwave UV light.Does not react to acids except to slowly dissolve, unlike dolomite and calcite.Also pyroelectric and piezoelectric. |
| Occurences | include Marysvale, Utah; Red Mountain, Custer County, Colorado and Goldfield district, Nevada, USA and Tolfa, Italy. |
| Indicators | crystal habit, color, non-reaction to acids and hardness. |
| DensityNote | average for translucent minerals |
| IMAStatus | Approved |
| Discovered | 1824 |
| CellParameters | a = 6.98c = 17.32 |
| Ratio | a:c = 1 : 2.481 |
| OpticalType | Uniaxial (+) |
| RI | n ω =1.572 n ε =1.592 |
| Birefringence | δ=0.020 |
| SurfaceRelief | Moderate |
| TypeLocality | Tolfa Rome Province Latium Italy |
| Strunz | 6/B.11-20 6 : SulphatesChromatesMolybdates B : Waterfree sulphates [SO4]2- with unfamiliar anions. cations of medium size 11 : Alunite groupNatroalunite - Jarosite - Beaverite |
