igneous
Pegmatite with Lepidolite and Feldspar
Pegmatite (containing K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2 and KAlSi3O8)
Hardness: 2.5-4 (Lepidolite) to 6 (Feldspar); Color: White, pink, lilac, and greyish-purple; Luster: Pearly to vitreous; Crystal structure: Monoclinic; Cleavage: Perfect basal cleavage in the mica portions.
- Hardness
- 2
- Color
- White, pink, lilac, and greyish-purple
- Luster
- Pearly to vitreous
Identified More igneous →
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Physical properties
Hardness: 2.5-4 (Lepidolite) to 6 (Feldspar); Color: White, pink, lilac, and greyish-purple; Luster: Pearly to vitreous; Crystal structure: Monoclinic; Cleavage: Perfect basal cleavage in the mica portions.
Formation & geological history
Formed during the final stages of a magma's crystallization, usually in intrusive igneous environments. These rocks are characterized by exceptionally large crystals due to the presence of volatiles like water and fluorine which allow for rapid ion movement.
Uses & applications
Source of lithium (from lepidolite) used in batteries and glass making; feldspar is used in ceramics and abrasives. Also valued by mineral collectors for its aesthetic crystalline inclusions.
Geological facts
Lepidolite is one of the major sources of the rare alkali metals rubidium and caesium. It was originally named 'lilalite' because of its lavender color, before being renamed from the Greek 'lepidos' for scale.
Field identification & locations
Identify by looking for large, light-colored crystals (feldspar/quartz) mixed with purple or pink platy/micaceous minerals (lepidolite). Commonly found in pegmatite districts such as those in Brazil, Madagascar, and the Southwestern United States.
