General Information: Chemical Formula:(Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2
Composition:(Molecular Weight = 1,032.43 gm)
Sodium 8.91 %
NaCalcium 7.76 %
CaAluminum 15.68 %
AlSilicon 16.32 %
SiSulfur 9.32 %
S Chlorine 1.72 %
ClOxygen 40.29 %
O Empirical Formula: Na4Ca2Al6Si6O22S2(SO4)Cl0.5
Environment:Igneous rocks low in silica and rich in alkalies.
Locality:Vesuvian lavas, on Mte Somma, Italy.
Name Origin:Named after the French crystallographer, R. J. Hauy (1743-1822).
Physical Properties: Cleavage:[110] Perfect, [011] Perfect, [101] Perfect
Color:blue, green, red, yellow, or gray.
Density:2.4 - 2.5, Average = 2.45
Diaphaniety:Subtransparent to translucent
Habits:Crystalline - Coarse - Occurs as well-formed coarse sized crystals., Twinning Common - Crystals are usually twinned., Euhedral Crystals - Occurs as well-formed crystals showing good e xternal form.
Hardness:5-6 - Between Apatite and Orthoclase
Luminescence:None.
Luster:Vitreous - Greasy
Streak:bluish white
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