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Aegirine-augite [abbr. Agt ]

Year of discovery: 1892 (World), 1917 (Japan)

Locality list: 99 localities of aegirine-augite

• (Ca,Na)(Fe³⁺,Mg,Fe²⁺)Si₂O₆
• [Ca²⁺,Na⁺][Fe³⁺,Mg²⁺,Fe²⁺][(SiO₃)₂]^4-
• CaMgFe/(CaMgFe+NaAlFe)=0.2-0.8

• Class: Ca-Na pyroxene group < Pyroxene supergroup
• Class: Inosilicate (Single chain)
• Variety: Blanfordite (+Mn)

• CaMgFe/(CaMgFe+NaAlFe) < 0.2: Aegirine (Series)
• CaMgFe/(CaMgFe+NaAlFe) > 0.8: Enstatite, Ferrosilite, Wollastonite

• Fe => Al: Omphacite (Series)

• Color: Green-Black
• Streak: White
• Luster: Vitrous

• Habit: Acicular, Pyramidal

• Cleavage: Perfect on {110} (2 planes), Parting on {100} (1 plane)
• Hardness: 6
• Density: 3.5

• System: Monoclinic
• Group: 2/m, C2/c
• Lattice: a=9.7, b=8.8, c=5.3, β=105.0