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Alunite (Photo) [abbr. Alu ]

Year of discovery: 1824 (Allumiere quarries, Italy), 1898 (Japan)

Locality list: 402 localities of alunite

• KAl₃(SO₄)₂(OH)₆
• [K⁺][Al³⁺₃][(OH)₆|(SO₄)₂]^10-

• Class: Alunite group < Alunite supergroup
• Class: Sulfate - Hydroxide
• Insoluble in: Water, HCl
• Fluorescence: UV excitation (White)
• Electrical: Pyroelectric (Strong)
• Radioactive: Very weak

• K => Na: Natroalunite, Natroalunite-2c
• K => NH₄: Ammonioalunite
• K => Ca_0.5: Huangite
• K => Ba_0.5: Walthierite

• Al => Fe: Jarosite

• Color: White-Yellowish brown
• Streak: White
• Luster: Vitreous
• Diaphaneity: Transparent-Translucent

• Habit: Granular, Platy

• Cleavage: Perfect on {0001} (1 plane), Indistinct on {0112} (3 plane)
• Hardness: 3.5-4
• Density: 2.8

• System: Trigonal
• Group: 3m, R3m
• Lattice: a=6.7, c=17.3