[ Top ] [ Japanese ]

Anorthite (Photo) [abbr. An ]

Year of discovery: 1823 (Monte Somma, Italy), 1879 (Japan)

Locality list: 227 localities of anorthite

• CaAl₂Si₂O₈
• (Ca,Na)Al(Al,Si)Si₂O₈
• [Ca²⁺][Al₂Si₂O₈]^2-

• Class: Plagioclase series < Feldspar group
• Class: Tecto-Aluminosilicate
• Soluble in: HCl (Decompose)
• Magnetism: Diamagnetic
• Old definition was CaAl/(NaSi+CaAl)=0.9-1.0
• Variety: CaAl/(NaSi+CaAl)=0.7-0.9, Bytownite
• Variety: CaAl/(NaSi+CaAl)=0.5-0.7, Labradorite
• Variety: Spectrolite (Iridescent labradorite)

• Polymorph: Dmisteinbergite (Hexagonal), Svyatoslavite (Monoclinic)

• Ca => Ba: Celsian, Paracelsian
• Ca => Sr: Slawsonite

• CaAl => (Na,K)Si: Anorthoclase
• CaAl => RbSi: Rubicline
• CaAl => NaSi: Albite(Series), Kumdykolite, Lingunite
• CaAl => KSi: Orthoclase, Adularia, Microcline, Sanidine

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

• Habit: Thick platy, Short prismatic

• Cleavage: Perfect on {001} (1 plane), Good on {010} (1 plane), Imperfect on {100} (1 plane)
• Hardness: 6-6.5
• Density: 2.7

• System: Triclinic
• Group: (-1), P(-1)
• Lattice: a=8.2, b=12.9, c=14.2, α=93.2, β=115.9, γ=91.2