Crystal Dioptase

Chemical Formula

Cu₆Si₆O₁₈ ·6H2O

Composition

Hydrous copper silicate

Color

Deep emerald green, dark green, bluish-green

Streak

Green

Hardness

5

Crystal System

Hexagonal

Crystal Forms 
and Aggregates

In distinct, hexagonally-shaped crystals with pointed, rhombohedral ends. Crystals are almost almost always doubly terminated, and are usually short and stubby, although they are occasionally prismaticand elongated. Crystals may also be more typical rhombohedral, though this habit is very uncommon. Crystals are usually in dense groups of interconnected crystals, but may be as isolated individuals. Also drusy, radiating, acicular, botryoidal, grainy, encrusting, and massive.
 

Transparency

Transparent to nearly opaque

Specific Gravity

3.3 - 3.4

Luster

Vitreous to adamantine

Cleavage

1,3

Fracture

Uneven

Tenacity

Brittle

In Group

Silicates; Cyclosilicates

Striking Features

Distinctive color and crystal habits

Environment

As a secondary mineral in hydrothermal replacement copper deposits.
 

Rock Type

Sedimentary, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

3

Demand (1-3)

1