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 % Na
Calcium 7.76 % Ca
Aluminum 15.68 % Al
Silicon 16.32 % Si
Sulfur 9.32 % S
Chlorine 1.72 % Cl
Oxygen 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
More details...