Crystal Chalcopyrite

Chemical Formula

CuFeS₂

Composition

Copper iron sulfide

Color

Brass yellow to golden yellow; sometimes dark brown to black. Tarnishes to a multicolored purple, blue, and red.

Streak

Black with a slightly green tinge

Hardness

3.5 - 4

Crystal System

Tetragonal

Crystal Forms 
and Aggregates

Crystals resemble tetrahedrons and octahedrons, but they are slightly asymmetrical and therefore are categorized in the tetragonal system. Also occurs massive, grainy, reniform, and as groups of small, distorted crystals. Crystals are commonly striated in different directions on different crystal faces.

Transparency

Opaque

Specific Gravity

4.1 - 4.3

Luster

Metallic

Cleavage

Indiscernible

Fracture

Uneven

Tenacity

Brittle

Other ID Marks

Tarnishes with an iridescent purple, blue, and red.

Complex Tests

Soluble in nitric acid, tingeing the solution blue

In Group

Simple Sulfides

Striking Features

Low hardness, crystal form, iridescent tarnish, and brittleness

Environment

In the sulfide zones of copper deposits, in hypothermal veins and mesothermal veins, hydrothermal replacement deposits, metamorphic schists, and in igneous intrusions and dikes.

Rock Type

Igneous, Sedimentary, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

1

Demand (1-3)

1