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.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Isometric. Crystals octahedral; also grains and masses.|
|Colors||Pale yellow to brown, reddish, green.|
|Luster||Vitreous to resinous.|
|Fracture||Subconchoidal to uneven. Brittle.|
|Hardness||5 - 5.5.|
|Specific Gravity||4.3 - 5.7; usually 5.5.|
|Cleavage||Octahedral (not always evident).|
|Transparency||Translucent to opaque.|
|Optics||N=1.93-1.94 if slightly metamict; also 1.98-2.02.|
|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.|
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.
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.
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.
Green Brazilian gems weighing less than 1 carat have appeared on the market. The potential exists there for larger stones.
- Smithsonian Institution (Washington, D.C): 3.7 (brown, Virginia).
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.