Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Lepidolite is a phyllosilicate mineral belonging to the mica group. It is characterized by its distinctive lilac, pink, or purple color, often occurring in scaly aggregates or tabular crystals. Its name is derived from the Greek words 'lepidos' (scale) and 'lithos' (stone), referring to its scaly appearance. It is a significant source of lithium and is often associated with other lithium-bearing minerals like spodumene and tourmaline in pegmatite environments.
How to Identify
- Color
- Typically lilac, pink, purple, or rose-red. Less commonly gray, yellowish, or colorless.
- Luster
- Vitreous to pearly on cleavage surfaces.
- Texture
- Often found in fine-grained, scaly aggregates, or as larger tabular to pseudohexagonal crystals. Can also be massive.
- Crystal Form
- Monoclinic, typically forming tabular to pseudohexagonal crystals, often with a platy or scaly habit. Can also be massive or granular.
- Cleavage
- Perfect basal cleavage (001), allowing it to be split into thin, flexible, elastic sheets.
- Geological Environment
- Primarily in lithium-rich granitic pegmatites, often associated with quartz, feldspar, spodumene, tourmaline, and beryl. Also found in high-temperature hydrothermal veins and greisens.
Key Facts
- Hardness: 2.5-3.5 on the Mohs scale
- Specific Gravity: 2.8-2.9 g/cm³
- Crystal System: Monoclinic
- Color: Lilac, pink, purple, rose-red, gray, yellowish, colorless
- Luster: Vitreous to pearly
- Transparency: Transparent to translucent
- Fracture: Uneven to splintery (not commonly observed due to perfect cleavage)
- Cleavage: Perfect basal cleavage (001)
- Composition: Potassium lithium aluminum fluorohydroxysilicate
Quick Check
- Color: Lilac, pink, purple
- Luster: Vitreous to pearly
- Streak: White
Physical Characteristics
- Crystal Habit: Tabular, pseudohexagonal, platy, scaly aggregates, massive, granular
- Cleavage Type: Perfect basal cleavage (001)
- Fracture Type: Uneven to splintery
- Tenacity: Flexible, elastic
- Luster Type: Vitreous to pearly
Formation
Lepidolite forms primarily in highly evolved granitic pegmatites, which are coarse-grained igneous rocks. It crystallizes from late-stage, lithium-rich hydrothermal fluids that are residual from the crystallization of large granitic intrusions. It can also occur in high-temperature hydrothermal veins and greisens.
Usage
Lepidolite is the most common lithium-bearing mineral and a significant ore of lithium. Lithium is crucial for rechargeable batteries (e.g., for electric vehicles, mobile phones), ceramics, glass, and aluminum production. It is also used in some psychiatric medications. Due to its attractive color and mica-like luster, it is sometimes used as an ornamental stone, for carvings, and in jewelry (though its softness limits its use).
Age Distribution
Typically found in pegmatites, which can range from Precambrian to Cenozoic in age, depending on the specific geological setting.
Where to Find
Brazil
Minas Gerais is a significant source, producing large quantities of lepidolite, often associated with other lithium minerals.
United States
Notable occurrences in California (San Diego County), Maine, and New Mexico.
Canada
Found in pegmatite deposits in Manitoba and Quebec.
Zimbabwe
Historically a major producer, particularly from the Bikita pegmatite.
Russia
Occurrences in the Ural Mountains and other regions.
Afghanistan
Known for fine specimens, often associated with tourmaline.
Finding Tips
Target Pegmatites
Focus your search on granitic pegmatite dikes, especially those known for lithium mineralization. Look for areas with coarse-grained igneous rocks.
Look for Associated Minerals
Lepidolite often co-occurs with quartz, feldspar, spodumene, tourmaline (especially elbaite), beryl, and amblygonite. The presence of these minerals can indicate a favorable environment.
Observe Color and Luster
Its distinctive lilac to purple color and pearly luster on cleavage surfaces are key identifiers. Look for scaly or platy aggregates.
Test Cleavage
Carefully test for its perfect basal cleavage. It should easily split into thin, flexible sheets, characteristic of micas.
Similar Rocks
Muscovite
KAl2(AlSi3O10)(OH)2
Also known as: Common Mica
Biotite
K(Mg,Fe)3AlSi3O10(OH)2
Also known as: Black Mica
Zinnwaldite
K(Fe,Li,Al)3(Al,Si)4O10(OH,F)2
Also known as: Lithium-Iron Mica
Scientific Classification
- Mineral Class
- Silicates
- Group
- Mica Group, Phyllosilicates
- Crystal System
- Monoclinic
- Chemical Formula
- K(Li,Al)3(Si,Al)4O10(F,OH)2
- Composition
- Potassium lithium aluminum fluorohydroxysilicate. The exact composition can vary, with Li and Al substituting for each other, and F and OH also varying.
Explore Lepidolite
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.