Tantalite ps Microlite Shigar Valley, Skardu District, Gilgit-Baltistan, Pakistan Cabinet, 11.5 x 7 x 4.6 cm © irocks

Chemical Formula: (Na,Ca)2Ta2O6(O,OH,F)
Locality: Isalnd of Uto, State of Stockholm, Sweden.
Name Origin: From the Greek mikros – “small” and lithos – “stone.”

Microlite is a pale-yellow, reddish-brown, or black isometric mineral composed of sodium calcium tantalum oxide with a small amount of fluorine (Na,Ca)2Ta2O6(O,OH,F) . Microlite is a mineral in the pyrochlore group that occurs in pegmatites and constitutes an ore of tantalum. It has a Mohs hardness of 5.5 and a variable specific gravity of 4.2 to 6.4. It occurs as disseminated microscopic subtranslucent to opaque octahedral crystals with a refractive index of 2.0 to 2.2. Microlite is also called djalmaite.

Microlite occurs as a primary mineral in lithium-bearing granite pegmatites, and in miarolitic cavities in granites. Association minerals include: albite, lepidolite, topaz, beryl, tourmaline, spessartine, tantalite and fluorite.

Microlite was first described in 1835 for an occurrence on the Island of Uto, State of Stockholm, Sweden. A type locality is the Clark Ledges pegmatite, Chesterfield, Hampshire County, Massachusetts. The name is from Greek mikros for “small” and lithos for “stone.”


Discovery date : 1835
Country of Origin : USA

Optical properties

Optical and misc. Properties: Subtranslucent to opaque
Refractive Index: from 1,93 to 2,02

Physical Properties

Cleavage: {111} Indistinct, {111} Indistinct, {111} Indistinct
Color: Yellowish brown, Reddish brown, Greenish brown, Green, Gray.
Density: 4.2 – 6.4, Average = 5.3
Diaphaneity: Subtranslucent to opaque
Fracture: Sub Conchoidal – Fractures developed in brittle materials characterized by semi-curving surfaces.
Hardness: 5-5.5 – Apatite-Knife Blade
Luminescence: Non-fluorescent.
Luster: Vitreous – Resinous
Magnetism: Nonmagnetic
Streak: light yellow

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Photos :

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Microlite Macoa, Alto Ligonha District, Zambezia Province, Mozambique Size: 2.4 x 2.1 x 1.5 cm (miniature) © danweinrich
Microlite Ipê Mine, Governador Valadares, Doce valley, Minas Gerais, Brazil Specimen weight:35 gr. Crystal size:to 0,3 cm Overall size:4 x 3,5 x 1,2 cm © minservice
Microlite, beryl and muscovite Tanno – San Giacomo valley – Chiavenna – Sondrio prov. – Lombardy – Italy Specimen weight:190 gr. Crystal size:mm. 2,5 Overall size: 70mm x 53 mm x 50 mm © minservice