Microlite Value, Price, and Jewelry Information

Triangle-cut microlite, 0.90 cts, 5.3 x 5.1 mm, Brazil. © The Gem Trader. Used with permission.

Microlite

Ranging in color from pale yellow to brown, reddish, and green, microlite cabochons are prized by collectors. Faceted gems are very beautiful but extremely rare.

Microlite Information

Data Value
Name Microlite
Formula (Na,Ca)2Ta2O6(O,OH,F)
Etymology From the Greek mikros for “small,” due to the small size of the crystals found at the original locality.
Occurrence Primary mineral in granite pegmatites.
Colors Pale yellow to brown, reddish, green.
Fracture Subconchoidal to uneven
Hardness 5-5.5
Cleavage Indistinct, Octahedral (not always evident)
Crystallography Isometric. Crystals octahedral; also grains and masses.
Refractive Index 1.93-2.02
Birefringence None.
Luminescence None.
Luminescence Present No
Absorption Spectrum Not diagnostic.
Pleochroism None.
Optics N=1.93-1.94 if slightly metamict; also 1.98-2.02. May show anomalous birefringence.
Luster Vitreous to resinous
Specific Gravity 4.3-5.7; usually 5.5.
Transparency Translucent to opaque.
microlite - Virginia

Microlite: Amelia Court House, Virginia (0.3). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Comments

As the name suggests, microlite crystals are small. Ranging from translucent to opaque, faceted gems over 4 carats in size would be extremely rare. However, gem carvers can cut massive brownish or reddish material into cabochons up to several inches long.

Microlite belongs to the pyrochlore mineral supergroup and, mineralogically speaking, constitutes a group itself of pyroclores with the element tantalum (Ta) predominant.

microlite - orange crystals

This crystal specimen measures 4 x 3 x 2.5 cm and features muscovites and tiny, golden orange microlites on albite. Ipe mine, Governador Valadares, Doce Valley, Minas Gerais, Southeast Region, Brazil. © Rob Lavinsky, www.iRocks.com. Used with permission.

Identifying Characteristics

Microlite has a streak color ranging from pale yellow to brown. However, don’t conduct streak testing on finished gems. Test material in inconspicuous spots as a last resort only.

Due to radiation exposure during formation, microlites may become metamict, losing their crystalline structure. This metamictization may also cause anomalous double refraction (ADR).

Sources

Brazil produces fine, sometimes gemmy, green crystals.

The Rutherford Mines in Amelia, Virginia also yield green and brown crystals, and gemmy specimens may reach a few inches in length.

Other notable gem-quality sources include the following locations:

  • United States: Colorado; Connecticut; Maine; Massachusetts; New Hampshire; South Dakota.
  • Western Australia; Finland; France; Greenland; Madagascar; Norway; Sweden.

Stone Sizes

Green Brazilian gems weighing less than 1 carat have appeared on the market, and the potential exists there for larger stones.

Generally, faceted gems weigh under 3 to 4 carats. A garnet-red microlite crystal found in 1885 weighed 4.4 carats in the rough and, when faceted, looked like a red zircon.

  • Smithsonian Institution (Washington, D.C): 3.7 (brown, Virginia).

Care

Some microlites may be slightly radioactive due to impurities of rare-earth elements (REE), therefore, faceters should take precautions to avoid inhaling or accidentally ingesting dust from cutting.

Store microlite jewelry and carvings separately from more commonly encountered gemstones, such as garnet, quartz, topaz, etc. With a hardness ranging from 5 to 5.5, microlites can suffer scratches from these harder materials as well as common objects like a steel file, so use protective settings for ring use. To clean, use a soft brush, mild detergent, and warm water. Consult our gemstone jewelry cleaning guide for more recommendations.

microlite - Brazil

Microlite: Brazil (0.14). Photo © Joel E. Arem, PhD, FGA. Used with permission.