“Petalite (Faceted),” 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, 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 | In LW pale orange (Wyoming) or buff (Maine). May be orange in X-rays. |
| 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. |
| 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. |
“Petalite,” Mogok, Myanmar. © Rob Lavinsky, www.iRocks.com. Used with permission.
A major source of lithium, the mineral petalite rarely occurs in gem-quality crystal form. Although colorless, glassy crystals can make stunning faceted jewelry pieces, beautiful pale gray, white, yellow, and pink stones can also be found. Gem cutters occasionally cab massive pink material from Namibia.
Included cab-cut petalites may show a weak chatoyancy or cat’s eye effect.
Crystal petalites are sometimes called castorites. See “Sources” below.
No known treatments.
Notable gem sources include:
“Petalite,” San Piero in Campo, Elba Island, Livorno Province, Tuscany, Italy. © Rob Lavinsky, www.iRocks.com. Used with permission.
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.
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. 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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