Mimetite Mineral Overview

• Mineral name: Mimetite
• Mineral class: Phosphate (apatite group)
• Chemical formula: Pb₅(AsO₄)₃Cl (lead arsenate chloride)
• Crystal system: Hexagonal
• Mohs hardness: 3.5–4
• Color range: Yellow, orange, brown, green
• Luster: Resinous to vitreous
• Streak: White
• Cleavage: Poor
• Fracture: Uneven to subconchoidal
• Specific gravity: Approximately 7.1–7.3 (very heavy)
• Transparency: Transparent to translucent
• Common locations: Mexico, Namibia, Morocco, United States
• Uses: Collector mineral
• Similar minerals: Pyromorphite, vanadinite

Naming and Classification

Mimetite is a lead arsenate mineral belonging to the apatite group, which includes:

• Pyromorphite (lead phosphate)
• Vanadinite (lead vanadate)

The name “mimetite” comes from the Greek mimetes, meaning “imitator,” because it:

• Closely resembles other minerals, especially pyromorphite

Physical and Optical Characteristics

Mimetite typically occurs as:

• Hexagonal prismatic crystals
• Barrel-shaped crystals
• Botryoidal or globular aggregates

Its color is often vibrant and attractive, including:

• Bright yellow
• Golden orange
• Brown or greenish tones

The luster is resinous to vitreous, giving it a slightly glossy, sometimes waxy appearance.

With a Mohs hardness of 3.5–4, it is relatively soft.

Crystal Habit (Key Feature)

Mimetite crystals are often:

• Short, hexagonal prisms
• Barrel-shaped or stubby
• Sometimes forming dense clusters

These habits closely resemble pyromorphite, making visual identification challenging.

Chemical Composition and Structure

Mimetite is composed of:

• Lead (Pb)
• Arsenate (AsO₄)
• Chlorine (Cl)

It has a structure similar to other apatite-group minerals, with:

• Channels that can accommodate different ions

This allows substitution between arsenate, phosphate, and vanadate in related minerals.

Formation and Geological Occurrence

Mimetite forms as a secondary mineral in oxidized lead deposits, particularly:

Oxidation Zones

• Weathering of primary lead ores like galena

Typical formation conditions include:

• Near-surface environments
• Oxidizing conditions
• Presence of arsenic

It is commonly associated with:

• Galena
• Cerussite
• Wulfenite

Common Locations

Mimetite is found in several notable regions:

• Mexico: Famous for bright yellow crystals (Durango)
• Namibia: Tsumeb Mine (high-quality specimens)
• Morocco: Abundant collector material
• United States: Arizona and other lead معدن regions

Mexican and Namibian specimens are especially prized.

Uses and Practical Significance

Mimetite has no industrial use due to its rarity and toxicity.

It is valued for:

Collector Mineral

• Bright colors
• Attractive crystal forms

Educational Use

• Example of the apatite group and mineral substitution

Safety Considerations

Mimetite contains lead and arsenic, so:

• Avoid inhaling dust
• Do not ingest
• Wash hands after handling

Polished or intact specimens are generally safe to display.

Similar and Related Minerals

Mimetite can resemble:

• Pyromorphite: Usually greener; contains phosphate instead of arsenate
• Vanadinite: Typically red and contains vanadate
• Wulfenite: Tabular crystals, more orange

Chemical testing is often needed for precise identification.

Identification Notes for Collectors

• Look for yellow to orange hexagonal crystals
• Note high density (feels heavy)
• Observe resinous luster
• Check moderate softness (3.5–4)
• Consider association with lead ore deposits

Mimetite is a lead arsenate mineral, recognized for its bright colors and hexagonal crystal forms, making it a highly attractive but chemically complex member of the apatite group.