Crystal Pyrite

Chemical Formula

FeS₂

Composition

Iron sulfide, sometimes containing small amounts of cobalt, nickel, silver, and gold

Color

Yellowish gray to gray. Some specimens oxidize and form a yellow-brown or iridescent film on exposedcrystal faces.

Streak

Black with a slightly green tinge

Hardness

6 - 6.5

Crystal System

Isometric

Crystal Forms 
and Aggregates

Pyrite can form in extremely well-crystallized examples of cubes, pyritohedrons, and octahedrons. Combinations of these forms also occur. An icosahedron formed from a combination of an octahedron and pyritohedron is also known. Pyrite crystals frequently form penetration twinning, especially in thecubic form. Cubes are sometimes elongated in rectangular form. Also occurs massive, radiating, grainy,flaky, drusy, mammilary, encrusting, nodular, tuberose, fibrous, in concretions, and as groups of small crystals. Pyrite crystals are frequently striated. 

Transparency

Opaque

Specific Gravity

4.9 - 5.2

Luster

Metallic

Cleavage

None

Fracture

Conchoidal

Tenacity

Brittle

Other ID Marks

Some specimens develop a yellow-brown film on crystal faces.

In Group

Sulfides; Simple Sulfides

Striking Features

Hardness, color, well shaped crystals, heaviness, and streak

Environment

Pyrite forms in all types of environments.

Rock Type

Igneous, Sedimentary, Metamorphic

Popularity (1-4)

1

Prevalence (1-3)

1

Demand (1-3)

2