Gem of the Month

Each month this section will feature either a topic of interest to gem lovers or one special gemstone with background on the material and its value.

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April, 2001

Petalite

This rare, colorless gem is seldom available, but a must-have for the collector and a nice looking, if somewhat delicate jewelry stone for those lucky enough to obtain a piece. The major sources for transparent facetable stones are Brazil and Namibia. Usually this gem is seen as small, somewhat included pieces, a large clean piece being exceptional. It is somewhat fragile and presents problems in cutting and polishing that further diminish its availability. Even rarer are the occasionally found cat'seye petalites. Protective settings are advised for jewelry use which should be limited to pendants, earrings or brooches. Ultrasonic or steam cleaning is risky.

Value:

The standard concerns apply here, clarity and size are foremost in determining value. More than in most stones, cutting is a strong value factor as difficulty of cutting limits the production of fancy cuts to experts.

Gemological Data:

Makeup: Lithium aluminum silicate

Crystal Structure: Monoclinic

Hardness: 6 - 6.5

Luster: Vitreous to pearly

Density: 2.42

RI: 1.50 -1.51

DR: .014

Fluorescence: yellowish orange under X-rays with phosphorescence

Cleavage: perfect in one direction, distinct in two directions

Stones Currently Available:

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