Pyromorphite Mineral Overview

• Mineral name: Pyromorphite
• Mineral class: Phosphate (apatite group)
• Chemical formula: Pb₅(PO₄)₃Cl (lead chlorophosphate)
• Crystal system: Hexagonal
• Mohs hardness: 3.5–4
• Color range: Green, yellow-green, brown, orange, rarely white
• Luster: Resinous to subadamantine
• Streak: White
• Cleavage: Poor
• Fracture: Uneven to subconchoidal
• Specific gravity: Approximately 6.5–7.0 (very high)
• Transparency: Transparent to translucent
• Common locations: Germany, United Kingdom, United States, China, Morocco
• Uses: Collector mineral, minor lead ore
• Similar minerals: Mimetite, vanadinite

Naming and Classification

Pyromorphite is a lead phosphate mineral belonging to the apatite group, which includes minerals with similar crystal structures but different chemical compositions.

The name comes from Greek:

• pyr = fire
• morphe = form

This refers to its ability to crystallize into new forms when melted and cooled, a property noted historically.

It is closely related to:

• Mimetite (Pb₅(AsO₄)₃Cl)
• Vanadinite (Pb₅(VO₄)₃Cl)

These minerals often look very similar and can be difficult to distinguish without analysis.

Physical and Optical Characteristics

Pyromorphite typically forms:

• Hexagonal prismatic crystals
• Barrel-shaped crystals
• Botryoidal or crust-like masses

Crystals are often small but can be well-formed and highly attractive.

Its most common and desirable color is bright green, though it can also appear:

• Yellow-green
• Brown
• Orange

The luster is often resinous, giving it a slightly waxy or glossy appearance. With a hardness of 3.5–4, it is relatively soft.

A notable feature is its high density, making it feel heavier than expected.

Chemical Composition and Structure

Pyromorphite is composed of:

• Lead (Pb)
• Phosphate groups (PO₄)
• Chlorine (Cl)

Its structure is similar to apatite minerals, forming a hexagonal framework that accommodates different anions (Cl, AsO₄, VO₄ in related minerals).

Formation and Geological Occurrence

Pyromorphite forms as a secondary mineral in the oxidized zones of lead ore deposits.

Typical formation conditions include:

• Weathering of primary lead minerals such as galena
• Interaction with phosphate-bearing solutions
• Low-temperature, near-surface environments

It is commonly associated with:

• Galena
• Cerussite
• Anglesite
• Limonite

These associations reflect oxidizing conditions in lead-rich deposits.

Common Locations

Pyromorphite is found in many classic mining regions:

• Germany: Historic localities with fine crystals
• United Kingdom: Cornwall and other lead mining areas
• United States: Pennsylvania, Arizona
• China and Morocco: Modern sources of high-quality specimens

Chinese and Moroccan specimens are especially popular in the collector market.

Uses and Practical Significance

Pyromorphite has limited industrial use but is important as:

Collector Mineral

• Highly valued for bright green color and crystal form

Minor Lead Ore

• Occasionally a secondary source of lead

Environmental Role

• Can immobilize lead in soils by forming stable mineral phases

Similar and Related Minerals

Pyromorphite is often confused with:

• Mimetite: Arsenate analogue, often more yellow
• Vanadinite: Typically red-orange and more hexagonal plates

Distinguishing them often requires:

• Chemical testing
• Subtle differences in color and crystal habit

Identification Notes for Collectors

• Look for bright green, barrel-shaped hexagonal crystals
• Note resinous luster and moderate softness (3.5–4)
• Check high density (feels heavy)
• Observe association with lead minerals
• Confirm identity if distinguishing from mimetite or vanadinite

Pyromorphite is a lead phosphate mineral, recognized for its vivid green color, distinctive barrel-shaped crystals, and formation in oxidized lead deposits, making it a favorite among mineral collectors.