Corundum

Al2O3

This specimen is a large, brownish-gray, barrel-shaped crystal of corundum, approximately 7.5 centimeters across, exhibiting its characteristic hexagonal habit.

Corundum Physical Properties

Mohs Hardness

Crystal System

trigonal

Luster

vitreous

Streak Color

white

Cleavage

none (parting common)

Fracture

conchoidal

Specific Gravity

3.95

Colors

brown, gray, blue, red, pink, yellow, green, purple, colorless

Transparency

transparent

Type Locality

Pennsylvania, USA

Mineral Group

Oxides

Uses

abrasives, gemstone, industrial, collector

Associated Minerals

feldspar, mica, garnet, spinel, kyanite

Rarity

uncommon

Geological Context

Corundum forms in aluminum-rich, silica-poor metamorphic rocks like schist, gneiss, and marble, as well as in some igneous rocks such as syenite and nepheline syenite. It can also be found in placer deposits due to its high hardness and resistance to weathering.

Back to Collection

Related Specimens

Bustamite

Jeremejevite

Rose Quartz

Crocoite

Bauxite

Carnelian