Lepidolite has a chemical composition that ranges in a solid solution series from that of polylithionite KLi2Al(Si4O10)(F,OH)2 to that of trilithionite K(Li1.5Al1.5)(AlSi3O10)(F,OH)2. This compositional range of lithium mica is known as the lepidolite series.
The properties of lepidolite make most specimens easy to identify. If you find a pink to purple mica mineral, it is probably lepidolite.
Mine Production Lepidolite: This photograph shows a small amount of crushed lepidolite produced from the Stewart Mine, San Diego County, California. It was removed from the mine in the form of compact masses of purplish-pink crystals as is characteristic of lepidolite. Particles in the photo are up to about one centimeter across. Photograph by the United States Geological Survey.
| Physical Properties of Lepidolite | |
| Chemical Classification | Silicate – Phyllosilicate |
| Color | Usually pink, red, or purple, often grayish. Rarely colorless or yellow. |
| Streak | White to colorless. Often sheds tiny flakes upon hardness testing. |
| Luster | Pearly to vitreous. |
| Diaphaneity | Transparent to translucent |
| Cleavage | Perfect in one direction. |
| Mohs Hardness | 2.5 to 3.5 |
| Specific Gravity | 2.8 to 3.0 |
| Diagnostic Properties | Cleavage, color, transparency, pseudohexagonal crystals. |
| Chemical Composition | K(Li,Al3)(AlSi3)O10(OH,F)2 |
| Crystal System | Monoclinic |
| Uses | Used as an ore of lithium. Crushed for use as flake mica. Used to make glass and enamel. Used as a minor gemstone. |