Alunite
Image: <bdi><a href="https://www.wikidata.org/wiki/Q56247090" class="extiw" title="d:Q56247090"><span title="mineral collector and dealer">Robert M. Lavinsky</span></a></bdi> (CC BY-SA 3.0)
Mineral NameAlunite
Chemical FormulaKAl₃(SO₄)₂(OH)₆
Mohs Hardness3.5
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavageperfect on {0001}
Fractureuneven
Specific Gravity2.65
Colorsyellowish-tan, beige
Transparencytranslucent
Type LocalityChang-Len level 3, Chinkuahshih Mine, Jui-Fang Town, Taipei County, Taiwan Province, Taiwan
Mineral GroupSulfates
Usesindustrial, collector
Associated Mineralspyrite, kaolinite, quartz
Rarityuncommon
Description
This specimen of alunite features a dense aggregate of elongated, blade-like crystals, exhibiting a yellowish-tan to beige color. The crystals are intergrown, forming a somewhat radiating or matted texture.
Geological Context
Alunite typically forms as a secondary mineral in hydrothermal alteration zones, often associated with volcanic rocks. It results from the reaction of acidic, sulfate-rich fluids with potassium-bearing minerals like feldspars.
