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Microlite
Current inventory: 2 gems
 

Chemistry:  BeAl₂O₄ + (Na,Ca)₂Ta₂O₆(O,OH,F)

Discovered in 1835;   IMA status: Valid (pre-IMA; Grandfathered).
Microlite gets its name is from the Greek words mikros meaning small, and lithos meaning stone; due to the very small size of the crystals found at the original locality.

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/C.18-10

4 : Oxides & Hydroxides
C : Oxides with metal : oxygen = 2:3 (M2O3 and related compounds)
18 : Pyrochlore group, Microlite series with Ta > Nb

Crystal Data

Crystallography:

Isometric - Hexoctahedral

Crystal Habit:

Commonly as euhedral to subhedral octahedra, modified by the dodecahedron, cube, to 8 cm; also granular, massive. Twinning: Rare, according to the spinel law, twin plane.

Physical Properties

Cleavage:

[111] Poor

Fracture:

Irregular, Uneven, Splintery, Sub-Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0 - 5.5

Density:

4.20 - 6.4 (g/cm³)

Radioactivity:

Not Radioactive

Optical Properties

Color:

Yellow, Pale yellow to reddish brown, sometimes emerald-green

Transparency:

Opaque to Translucent, Transparent in thin fragments

Luster:

Vitreous to Adamantine, Resinous on fractures

Refractive Index:

1.93 - 2.02  Isotropic

Birefringence:

0.00 (Isotropic)

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

A primary mineral in lithium-bearing granite pegmatites, or replacing tantalum minerals; in miarolitic cavities in granites.

Type Locality:

Clark Ledges pegmatite locality, Chesterfield, Hampshire Co., Massachusetts, USA

Year Discovered:

1835

View mineral photos:

Microlite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Microlite is a very rare member of the Pyrochlore group of minerals. As a mineral, it is usually opaque to translucent and plentiful in some locations. Gem quality crystals however are quite rare and very small so faceted gems tend to be small and are extremely rare. Microlite is a beautiful gem that is found in colors of pale to bright yellow, brown, reddish and green. Current sources of gem grade Microlite are the Alto do Giz pegmatite, and Virgem da Lapa, Minas Gerais, Brazil.  

  
Microlite gems for sale: