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Lepidolite

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Lepidolite is Earth’s most common lithium-bearing mineral. Although typically pale lilac, specimens can also be colorless, violet, pale yellow, or gray. Lepidolite crystals may appear pseudohexagonal. The mineral is also found as botryoidal or kidneylike masses and fine- to coarse-grained, interlocking plates. Its perfect cleavage yields thin, flexible sheets. Lepidolite occurs in granitic pegmatites, where it is associated with other lithium minerals, such as beryl and topaz. The mineral is economically important as a major source of lithium, which is used to make glass and enamels. It is also a major source of the rare alkali metals rubidium and cesium.

Name: From the Greek lepidos for scale, in allusion to its micaceous structure.

Polymorphism & Series: 1M, 2M2 ; 3A polytypes common; 2M1 ; 3M2 rare; a group name.

Mineral Group: Mica group.

Crystallography: Monoclinic; prismatic. Crystals usually in small plates or prisms with hexagonal outline. Commonly in coarse- to finegrained scaly aggregates.

Lepidolite Composition: A fluosilicate of potassium, lithium, aluminum, K2Li3Al4Si7 0 2 i(0 H,F)3. Magnesium may be present.

Diagnostic Features: Characterized chiefly by its micaceous cleavage and usually by its lilac to pink color. Muscovite may be pink, or lepidolite white, and therefore a flame test should be made to distinguish the two.

Chemical Properties of Lepidolite

Chemical Classification Phyllosilicate
Chemical Composition K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2

Physical Properties of Lepidolite

Color Pink, purple, rose-red, violet-gray, yellowish, white, colorless
Streak White
Luster Sub-Vitreous, Resinous, Greasy, Pearly
Cleavage Perfect {001} perfect
Diaphaneity Transparent, Translucent
Mohs Hardness 2.5 – 4 on Mohs scale
Diagnostic Properties Cleavage
Crystal System Monoclinic
Tenacity Elastic
Fracture Micaceous
Density 2.8 – 2.9 g/cm3 (Measured)    2.83 g/cm3 (Calculated

Optical Properties of Lepidolite

Color / Pleochroism Colorless
Optical Extinction 3-10o
2V: 0° – 58°
Twinning Rare, composition plane f001g, twin axis [310].
Optic Sign Biaxial ({)
Dispersion: r > v; weak.

Occurrence

Lepidolite is a comparatively rare mineral, found in pegmatite dikes, usually associated with other lithium-bearing minerals such as pink and green tourmaline, amblygonite, spodumene. Often intergrown with muscovite in parallel position. Notable foreign localities for its occurrence are the Ural Mountains, U.S.S.R.; Isle of Elba; Rozna, Moravia; Madagascar. In the United States is found in western Maine at Hebron, Auburn, Norway, Paris, Rumford; near Middletown, Connecticut; Pala, San Diego County, California.

Association: Spodumene, elbaite, amblygonite, columbite, cassiterite, topaz, beryl, micas

Lithium battery

Uses

Extracted from lepidolite, the metal lithium has many industrial uses, such as in lithium batteries.

A source of lithium compounds.

Distribution

  • Czech Republic.
  • From Alabashka, Ural Mountains, Russia.
  • Sweden.
  • In the USA, at Mt. Mica, near Paris, Oxford Co., and Auburn, Androscoggin Co., Maine; in the MesaGrande and Pala districts, San Diego Co., California; from the Brown Derby pegmatite, Gunnison Co., Colorado; in the Ingersoll mine, near Keystone, Pennington Co., South Dakota.
  • From the Tanco mine, Bernic Lake, Manitoba, Canada.
  • At Maharitra, Mt. Bity, Madagascar. From Bikita, Zimbabwe.
  • In India, at Hazaribagh, Bihar.
  • From the Virgem da Lapa pegmatite, Minas Gerais, Brazil.

References

  • Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
  • Dana, J. D. (1864). Manual of Mineralogy… Wiley.
  • Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
  • Mindat.org. (2019). Lepidolite: Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
Cite this article as: Mahmut Mat, "Lepidolite", in Geology Science, [online] Accessed 21st August 2019, Available at: http://geologyscience.com/minerals/lepidolite/
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