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Sanidine (Photo) [abbr. Sa ]

Year of discovery: 1808 (Drachenfels, Germany), 1877 (Japan)

Locality list: 71 localities of sanidine

• KAlSi₃O₈
• (K,Na)(Si,Al)₄O₈
• [K⁺][AlSi₃O₈]^-
• Si-Al is disordered. Formed above 650 degree.

• Class: Alkaline Feldspar subgroup - Feldspar group
• Class: Tecto-Aluminosilicate
• Radioactive: Very weak

• Polymorph: Orthoclase (Monoclinic, Formed between 300-650 degree, Intermediately ordered Si-Al)
• Polymorph: Adularia (Monoclinic, Formed between 300-650 degree, Intermediately ordered Si-Al, Rhombic)
• Polymorph: Microcline (Triclinic, Formed below 300 degree, Ordered Si-Al by annealing)

• K => (Na,K): Anorthoclase
• K => Rb: Rubicline
• K => Na: Albite, Kumdykolite, Lingunite

• KSi => CaAl: Anorthite, Dmisteinbergite, Svyatoslavite
• KSi => BaAl : Celsian, Paracelsian
• KSi => SrAl: Slawsonite

• Color: Colorless, White
• Streak: White
• Luster: Vitreous
• Diaphaneity: Transparent-Translucent

• Habit: Thick tabular

• Cleavage: Perfect on {001} (1 plane), Distinct on {010} (1 plane), Parting on {100} (1 plane)
• Hardness: 6
• Density: 2.6

• System: Monoclinic
• Group: 2/m, C2/m
• Lattice: a=8.6, b=13.0, c=7.2, β=116.0

Etymology: Sanin (Board) in Greek