Crystal K2 Rough

Chemical Formula

Al₂SiO₅

Composition

Aluminum silicate

Color

Light to dark blue, indigo-blue. Sometimes multicolored with different shades of blue or white, or with color streaks or stripes. A frequent habit is a deeper colored blue streak running through the center of a crystal. Less commonly colorless, white, gray, green, orange, or black.

Streak

Colorless

Hardness

4.5 - 7

Crystal System

Triclinic

Crystal Forms 
and Aggregates

Most often in long and slender bladed crystals. Also in bladed crystal groups, radiating, in veins,reticulated, and in flattened tabular crystals. Rarely twinned in v-shaped butterfly twins.

Transparency

Transparent to translucent

Specific Gravity

3.5 - 3.7

Luster

Vitreous

Cleavage

1,1;2,1

Fracture

Splintery

Tenacity

Brittle

In Group

Silicates; Nesosilicates

Striking Features

Different direction hardness and color.

Environment

In metamorphosed schists and gneisses. Also in granite pegmatites.

Rock Type

Igneous, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

2

Demand (1-3)

2