Microlite Value, Price, and Jewelry Information

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

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 Value

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Microlite Information

DataValue
NameMicrolite
Crystallography Isometric. Crystals octahedral; also grains and masses.
Refractive Index 1.93-2.02
Colors Pale yellow to brown, reddish, green.
Luster Vitreous to resinous.
Fracture Subconchoidal to uneven
Hardness 5-5.5
Specific Gravity 4.3-5.7; usually 5.5.
Birefringence None.
Cleavage Octahedral (not always evident)
Luminescence None.
Transparency Translucent to opaque.
Absorption Spectrum Not diagnostic.
Formula(Na,Ca)2Ta2O6(O,OH,F)
Pleochroism None.
Optics N=1.93-1.94 if slightly metamict; also 1.98-2.02. May show anomalous birefringence.
EtymologyFrom the Greek mikros for “small,” due to the small size of the crystals found at the original locality.
OccurrencePrimary mineral in granite pegmatites.
microlite - Virginia
“Microlite,” Amelia Courthouse, Amelia County, Virginia, USA. © Rob Lavinsky, www.iRocks.com. 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. Mineralogically speaking, microlite is a group itself, consisting of pyroclores with the element tantalum (Ta) predominant.

Identifying Characteristics

Microlite has a streak color ranging from pale yellow to brown. Please note: 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 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. Gemmy specimens may reach a few inches in length.

Other notable gem-quality sources include:

  • United States: Colorado; Connecticut; Maine; Massachusetts; New Hampshire; South Dakota.
  • Western Australia; Finland; France; Greenland; Madagascar; Norway; Sweden.
microlite - orange crystals
This specimen measures 4 x 3 x 2.5 cm and features microlite and muscovite on albite. Which crystals are the microlites? The tiny golden-orange ones. “Microlite,” Ipe mine, Governador Valadares, Doce valley, Minas Gerais, Southeast Region, Brazil. © Rob Lavinsky, www.iRocks.com. Used with permission.

Stone Sizes

Green Brazilian gems weighing less than 1 carat have appeared on the market. 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. When faceted, the stone looked like a red zircon.

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

Care

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. 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.