Bazzite

Bazzite
Bazzite from Fibbia mountain, Fontana, Central St Gotthard Massif, Leventina, Ticino, Switzerland
General
Category	Cyclosilicate
Formula (repeating unit)	Be3Sc2Si6O18
Strunz classification	9.CJ.05
Crystal system	Hexagonal
Crystal class	Dihexagonal dipyramidal (6/mmm) H-M symbol: (6/m 2/m 2/m)
Space group	P6/mcc
Unit cell	a = 9.521 Å, c = 9.165 Å; Z = 2
Identification
Color	Light to dark sky-blue, blue green
Crystal habit	Aggregates of subparallel prisms
Cleavage	Indistinct on {0001}
Fracture	Irregular
Tenacity	Brittle
Mohs scale hardness	6.5 - 7
Luster	Vitreous
Streak	Pale bluish white
Diaphaneity	Semitransparent
Specific gravity	2.77 - 2.85
Optical properties	Uniaxial (-)
Refractive index	nω = 1.622-1.637 nε = 1.602-1.622
Birefringence	0.0210
Pleochroism	O = pale greenish yellow; E = intense sky-blue
References

Bazzite is a beryllium scandium cyclosilicate mineral with chemical formula: Be₃Sc₂Si₆O₁₈ (Be₃(Sc,Fe)₂Si₆O₁₈ or Be₃(Sc,Al)₂Si₆O₁₈). It crystallizes in the hexagonal crystal system typically as small blue hexagonal crystals up to 2 cm length. It has a Mohs hardness of 6.5-7 and a specific gravity of 2.77 to 2.85.

It is hard to distinguish from blue beryl.

Occurs in miarolitic cavities in granite, in alpine veins and in scandium bearing granitic pegmatites. It occurs associated with quartz, orthoclase, muscovite, laumontite, albite, hematite, calcite, chlorite, fluorite, beryl and bavenite.

It was first described from an occurrence in Baveno, Italy. Named after the discoverer, the Italian engineer Alessandro E. Bazzi.