Faceted petalite, 13.35 cts, Pech, Kunar Province, Afghanistan. © Rob Lavinsky, www.iRocks.com. Used with permission.
Gem-quality, colorless, facetable petalite is rare and desirable to collectors. More so if the stones are large and free of inclusions.
| Data | Value |
|---|---|
| Name | Petalite |
| Crystallography | Monoclinic. Crystals rare, tabular; usually massive, cleavable. |
| Refractive Index | 1.503-1.523 |
| Colors | Colorless, white, gray, yellow, brown, sometimes reddish or greenish white, pink. |
| Luster | Vitreous to pearly |
| Hardness | 6-6.5 |
| Fracture | Conchoidal |
| Specific Gravity | 2.3-2.5 |
| Birefringence | 0.012-0.014 |
| Cleavage | Perfect 1 direction |
| Luminescence | Some specimens may fluoresce. In LW pale orange (Wyoming) or buff (Maine). May be orange in X-rays. Thermoluminescence. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long, X-ray Colors |
| Transparency | Translucent to transparent |
| Absorption Spectrum | Not diagnostic; some stones may show a vague band at 4540. |
| Phenomena | Chatoyancy, color change. |
| Formula | LiAlSi4O10 |
| Optics | a = 1.503-1.510; β =1.510-1.521; γ = 1.516-1.523. Biaxial (+), 2V = 83°. |
| Optic Sign | Biaxial + |
| Etymology | From the Greek petalos for “leaf,” in allusion to its cleavage. |
| Occurrence | In granite pegmatites, in crystals and masses. |
| Pleochroism | None |
Petalite, 4.3 x 4.2 cm, Rubicon Mine, Okongava Ost Farm 72, Karibib Constituency, Erongo Region, Namibia. Photo by John Sobolewski. Licensed under CC by 3.0.
A major source of lithium, the mineral petalite rarely occurs in gem-quality crystal form.
Just below quartz in hardness and with perfect cleavage, petalites are best suited for earrings and pendants. These jewelry pieces receive minimal physical impact. Avoid ring use without a protective setting.
Sterling silver earrings featuring petalite and white diamond. Photo courtesy of liveauctioneers.com and Dalshire International.
Although colorless, glassy crystals can make stunning faceted jewelry pieces, beautiful pale gray, white, yellow, greenish, and pink stones can also be found. Gem cutters occasionally cab or carve massive pink material from Namibia.
Carved petalite pelican on a green marble base, 4.25″ x 3.5”. Photo courtesy of liveauctioneers.com and B.S. Slosberg, Inc. Auctioneers.
Included cab-cut petalites may show a weak chatoyancy or cat’s eye effect.
Some petalites from Myanmar may show a color change effect between daylight and artificial light.
This keystone step-cut petalite appears yellow-greenish in daylight but golden brown under other light sources. 2.19 cts, 9 x 8.4 mm, Myanmar. © The Gem Trader. Used with permission.
Crystal petalites are sometimes called castorites. When the mineral pollucite was discovered in Elba, Italy in 1846, it was named after Pollux, the twin brother of Castor in Classical mythology. The discoverers associated it with castorite, named after Castor, since both occurred in lithium-rich granite pegmatites at this source. Although castorite was later renamed petalite, the name pollucite remained unchanged.
Crystals of petalite, such as this specimen from Elba Island, Italy, were once called “castorites.” © Rob Lavinsky, www.iRocks.com. Used with permission.
Scientists have synthesized petalite for various commercial purposes. However, there is no known jewelry use for this material. There are also no known gem treatments for petalites.
Notable gem sources include the following:
Faceted petalites are usually small. You can find faceted gems from Brazil for sale, ranging from 1 to 10 cts. Rough can range up to 20 cts. Some Brazilian and Namibian rough material has yielded somewhat larger stones in the 50-ct range.
Store your petalites separately from other harder gems to avoid scratching. Use a soft brush, mild detergent, and warm water for cleaning. Consult our gemstone jewelry cleaning guide for more recommendations.
Petalite: Brazil (15.65). Photo © Joel E. Arem, PhD, FGA. Used with permission.
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