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Lepidolite
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Lepidolite was named in 1792 by Martin Klaproth from the Greek words lepidos for scale, and lithos for stone, in allusion to its micaceous structure.

Discovered in 1792; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

K(Li,Al)₃(Si,Al)₄O₁₀(F,OH)₂

Potassium Lithium Aluminum Silicate Hydroxide Fluoride

Molecular Weight:

388.30 gm

Composition:

Potassium

10.07 %

K

12.13 %

K₂O

Lithium

3.58 %

Li

7.70 %

Li₂O

Aluminum

6.95 %

Al

13.13 %

Al₂O₃

Silicon

28.93 %

Si

61.89 %

SiO₂

Hydrogen

0.26 %

H

2.32 %

H₂O

Oxygen

45.32 %

O

Fluorine

4.89 %

F

4.89 %

F

— %

F

—2.06 %

—O=F₂

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/H.10-70

Nickel-Strunz 10th Ed. ID:

9.EC.15

9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets

Related to:

Mica Group. Biotite Subgroup. Muscovite, Phlogopite, Polylithionite-Trilithionite Series

Members of Group:

Mica Group: Aluminoceladonite, Anandite, Annite, Annite-Phlogopite Series, Aspidolite, Balestraite, Biotite, Bityite, Boromuscovite, Brammallite, Celadonite, Chernykhite, Chromceladonite, Chromphyllite, Clintonite, Eastonite, Ephesite, Ferroaluminoceladonite, Ferroceladonite, Ferrokinoshitalite, Fluorannite, Fluorphlogopite, Ganterite, Glauconite, Hendricksite, Illite, Kinoshitalite, Lepidolite, Luanshiweiite, Margarite, Masutomilite, Montdorite, Muscovite, Muscovite-Celadonite Series, Nanpingite, Natro-glauconite, Norrishite, Oxykinoshitalite, Oxyphlogopite, Paragonite, Phengite, Phlogopite, Polylithionite, Preiswerkite, Roscoelite, Shirokshinite, Shirozulite, Siderophyllite, Sokolovaite, Suhailite, Tainiolite, Tetraferriannite, Tetraferriphlogopite, Tobelite, Trilithionite, Voloshinite, Wonesite, Yangzhumingite, Zinnwaldite

Varieties:

Cs-rich Lepidolite, Rb-rich Lepidolite

Synonyms:

Flower Sugilite, Lavenderine, Lilalite, Lilianthite, Lithia Mica, Lithionglimmer, Lithionite

Crystal Data

Crystallography:

Monoclinic

Crystal Habit:

Tabular to prismatic pseudohexagonal crystals, commonly with rounded terminal faces, to 20 cm. In coarse to fine scaly aggregates and massive.

Twinning:

Rare, composition plane {001}, twin axis [310]

Physical Properties

Cleavage:

Perfect {001}

Fracture:

Uneven

Tenacity:

Flexible, elastic

Moh's Hardness:

2.5 - 4.0

Density:

2.80 - 2.90 (g/cm³)

Luminescence:

May fluoresce medium intensity of creamy white to pale yellow; sometimes yellow

Radioactivity:

Barely Detectable; GRapi = 143.68 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Pink, purple, rose-red, violet-gray, blue, yellowish, white, colorless; colorless to pale pink in thin section

Transparency:

Translucent

Luster:

Vitreous, Pearly

Refractive Index:

1.525 - 1.587  Biaxial ( - )

Birefringence:

0.0290 - 0.0380

Dispersion:

Weak; r > v

Pleochroism:

X = almost colorless; Y = Z = pink, pale violet

Occurances

Geological Setting:

In granite pegmatites, derived by metasomatic replacement of muscovite or biotite; in some high-temperature quartz veins, greisens, and granites.

Common Associations:

Spodumene, Elbaite, Amblygonite, Columbite, Cassiterite, Topaz, Beryl, Micas

Type Locality:

Rožná pegmatite, Ždár nad Sázavou, Vysocina Region, Moravia (Mähren; Maehren), Czech Republic

Year Discovered:

1792

View mineral photos:

Lepidolite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Lepidolite was once considered to be a distinct mineral species but has been redefined by the IMA as a group of minerals and as part of the Polylithionite-Trilithionite Series. The name Lepidolite is also used loosely as a term for any light colored lithium-bearing mica that has not been sufficiently analyzed for species determination (ie., some "Lepidolite" may actually be Muscovite or Phlogopite). Lepidolite is a member of the Mica Group of minerals that also includes Celadonite, Muscovite, Phlogopite and Polylithionite.

Lepidolite is an uncommon mica and is an ore of lithium that forms in huge masses that can contain substantial amounts of lithium. Its typical pink to violet colors are one of the only field tests to identify Lepidolite from other micas although pink Muscovite or very pale Lepidolite may complicate identification.

Lepidolite is available from Rozná, near Bystrice, Czech Republic; from Alabashka, Ural Mountains, Russia. In the Varuträsk pegmatite, 15 km northwest of Skellefteå, Västerbotten, Sweden. In the USA, at Mt. Mica, near Paris, Oxford County, and Auburn, Androscoggin County, Maine; in the Mesa Grande and Pala districts, San Diego County, California; from the Brown Derby pegmatite, Gunnison County, Colorado; in the Ingersoll mine, near Keystone, Pennington County, 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.
 

  
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