Crystal Pyromorphite

Chemical Formula

Pb₅(PO₄)₃Cl

Composition

Lead chloro-phosphate. The phosphate radical (PO₄) may be partially replaced by an arsenate radical (AsO₄), thus forming a series with Mimetite.

Variable Formula

Pb₅([P,As]O₄)₃Cl

Color

Light to dark green, yellow-green, greenish-white, brownish-green, brown, orange, gray, and white. May also be multicolored green and orange.

Streak

White

Hardness

3.5 - 4

Crystal System

Hexagonal

Crystal Forms 
and Aggregates

Occurs as barrel-like hexagonal crystals, which are usually grouped together in interesting aggregates, and may be bipyramidal. Also acicular, crusty, grainy, radiating, reniform, botryoidal and in curvy aggregates. Some larger crystals may be hollowed out on the ends or have a hopper growth pattern.

Transparency

Translucent

Specific Gravity

6.9 - 7.1

Luster

Resinous to greasy

Cleavage

None

Fracture

Subconchoidal to uneven

Tenacity

Brittle

Complex Tests

Dissolves in nitric acid

In Group

Phosphates; True Phosphates; Apatite Group

Striking Features

Color, hollow crystals, crystal habits, and localities

Environment

As a secondary mineral in the oxidation zone of lead ore deposits.

Rock Type

Sedimentary, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

3

Demand (1-3)

1