Wollastonite

Wollastonite from Brazil

Wollastonite is a calcium inosilicate mineral that may contain small amounts of iron, magnesium and manganese substituting for calcium.
It is usually white.
It forms when impure limestone or dolomite is subjected to high temperature and pressure and sometimes occurs in the presence of silica bearing fluids as in skarns or in contact with metamorphic rocks.
Has acicular nature.
Properties: high brightness and white coloration, low moisture and oil absorption, low volatile content.

Uses:
Primarily in ceramics, friction products, paint filter, plastics, cement, flux for welding.

Characteristics:
Category Inosilicate mineral ; Calcium silicate
Formula CaSiO3
Calcium 34,50%; Silicon 24,18%; Oxygen 41,32%
Crystal system Triclinic
Color: white, colorless, gray
Habit: rare as tabular crystals, commonly massive in lamellar, radiating
Cleavage perfect in two directions at near 90 degree angle
Hardness: 4,5-5
Fracture splintery to uneven
Lustero vitreous or dull to pearly on cleavage surface
Streak white
Transparent to translucent
Specific gravity 2,86-3,09
Density 2,8-2,9
Rock type metamorphic.
Optical properties biaxial (-)
Melting point 1540 degree Celsius
Soluble in HCl, Insoluble in water
Usually fluorescent yellow, orange or white.
Has yellow orange color in short wave with strong intensity and white, bluish white, yellow or orange under sort wave UV
Can have thermoluminescence
Main activator is Mn replacing Ca 555-560nm; 580nm; 603, 640 nm
Fe replacing Si 690-700 nm
Cr 720, 794, 840 nm

Common mineral associations: Calcite, Grossular, Vesuvianite, Diopside, Epidote, garnet, tremolite, feldspar, pyroxene.

Varieties:
Ferrowollastonite - gray or brown, iron rich variety of wollastonite with iron replacing the calcium and formula (Ca,Fe)SiO3
Manganowollastonite - light pink, manganese rich variety of Wollastonite, with manganese partially replacing the calcium, formula (Ca,Mn)SiO3

Distinguishing similar minerals:
Tremolite - has different cleavage angles, otherwise can be difficult to distinguish
Pectolite - crystals more compact and densely fibrous and usually in different environment than Wollastonite

Associated minerals: garnet, vesuvianite, diopside, tremolite, epidote, feldspar, pyroxene, calcite.

Other manes: wollastonite wollastonit wollastonitul wolastonite wolastonitul wolastonit