Schorl | |
Chemical Formula |
(Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6(BO3)3(Si,Al,B)6O18(OH,F)4[1][2] |
Species |
Silicates |
Crystal System |
Trigonal |
Mohs Scale |
7 |
Specific Gravity |
3.06 |
Color |
Most commonly black, but can range from brown, Purple, green, pink, or in a dual-colored pink and green. |
Streak |
White |
Luster |
Vitreous, Resinous |
Refractive Index |
n = 1.660 - 1.672 n = 1.635 - 1.650 |
Diaphaneity |
Translucent, Opaque |
Cleavage |
Poor/IndistinctVery poor on , |
Fracture |
Irregular/Uneven, Sub-Conchoidal |
Crystal Habit:Parallel and elongated. Acicular prisms, sometimes radiating. Massive. Scattered grains (in granite). | |
Geological Setting:In granites and granitic pegmatites, high temperature hydrothermal veins, metamorphic rocks. |