Lepidolite Mineral Overview

• Mineral name: Lepidolite
• Mineral class: Silicate (phyllosilicate, mica group)
• Chemical formula: K(Li,Al)₃(Si,Al)₄O₁₀(F,OH)₂
• Crystal system: Monoclinic
• Mohs hardness: 2.5–3
• Color range: Lilac, purple, pink, gray
• Luster: Pearly to vitreous
• Streak: White
• Cleavage: Perfect (one direction)
• Fracture: Uneven
• Specific gravity: Approximately 2.8–2.9
• Transparency: Transparent to translucent
• Common locations: Brazil, United States, Madagascar, Russia
• Uses: Lithium source, gemstone, ornamental stone
• Similar minerals: Muscovite, biotite, zinnwaldite

Naming and Classification

Lepidolite is a lithium-rich mica mineral, belonging to the mica group of phyllosilicates.

The name comes from Greek:

• lepidos = scale

This refers to its tendency to occur in scaly, flaky masses, typical of mica minerals.

It is one of the most important natural sources of:

• Lithium (Li)

Physical and Optical Characteristics

Lepidolite typically occurs as:

• Scaly or flaky masses
• Fine-grained aggregates
• Rare tabular crystals

Its most recognizable feature is its soft purple to lilac color, which may appear:

• Pinkish-lavender
• Light violet
• Grayish-purple

The luster is pearly on cleavage surfaces and vitreous on crystal faces.

With a Mohs hardness of 2.5–3, it is very soft and can be easily scratched or split.

Cleavage (Key Feature)

Like all micas, lepidolite exhibits:

• Perfect basal cleavage

This allows it to be:

• Easily split into thin, flexible sheets

Color Origin

The purple and pink coloration is caused by:

• Lithium content
• Trace elements such as manganese

These elements give lepidolite its distinctive pastel tones.

Chemical Composition and Structure

Lepidolite is composed of:

• Potassium (K)
• Lithium (Li)
• Aluminum (Al)
• Silicon (Si)
• Fluorine (F) and hydroxyl (OH)

It has a sheet silicate (phyllosilicate) structure, forming:

• Thin, layered sheets
• Weak bonding between layers

This structure explains its softness and cleavage.

Formation and Geological Occurrence

Lepidolite forms in granitic pegmatites, particularly in:

Lithium-Rich Pegmatites

• Late-stage crystallization of magma
• Enrichment in rare elements

Typical formation conditions include:

• High concentrations of lithium and fluorine
• Slow cooling of magma

It is commonly associated with:

• Spodumene
• Tourmaline
• Quartz
• Feldspar

These associations indicate rare-element pegmatite environments.

Common Locations

Lepidolite is found in several important regions:

• Brazil: Major source of lithium minerals
• United States: California, South Dakota
• Madagascar: High-quality specimens
• Russia: Pegmatite deposits

Brazil and Madagascar are especially known for colorful material.

Uses and Practical Significance

Lepidolite is important for:

Lithium Production

• Source of lithium used in:
  • Batteries
  • Ceramics
  • Glass

Gemstone and Ornamental Use

• Cabochons and carvings
• Decorative stone

Collector Mineral

• Attractive color and mica texture

Similar and Related Minerals

Lepidolite can resemble:

• Muscovite: Lighter, silvery color
• Biotite: Darker, black mica
• Zinnwaldite: Lithium-bearing mica with darker tones

Color and lithium content help distinguish lepidolite.

Identification Notes for Collectors

• Look for purple or lilac flaky material
• Note soft hardness (2.5–3)
• Observe perfect sheet-like cleavage
• Feel smooth, flexible layers
• Consider association with pegmatites

Lepidolite is a lithium-rich mica mineral, recognized for its distinctive purple coloration and flaky structure, making it both an important lithium source and a popular ornamental and collector stone.