“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.
Petalite Value
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Petalite Information
| Data | Value |
| Name | Petalite |
| Crystallography | Monoclinic. Crystals rare, tabular; usually massive, cleavable. |
| Colors | Colorless, white, gray, yellow, sometimes reddish or greenish white, pink. |
| Luster | Vitreous to pearly. |
| Fracture | Conchoidal, brittle. |
| Hardness | 6-6.5. |
| 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. |
| Spectral | Not diagnostic; some stones may show a vague band at 4540. |
| Transparency | Translucent to transparent |
| Phenomena | Chatoyancy |
| Formula | LiAlSi4O10 |
| Optics | a = 1.503-1.510; β =1.510-1.521; γ = 1.516-1.523. Biaxial (+), 2V: 83°. |
| 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.
Comments
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.
Enhancements
No known treatments.
Sources
Notable gem sources include:
- Utö, Sweden: the type locality
- United States: San Diego County, California; Greenwood, Maine; Bolton, Massachusetts; North Bonneville, Wyoming.
- Elba, Italy: When the mineral pollucite was discovered here 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.
- Londonderry, Western Australia: facetable material.
- Arassuahy, Brazil: large, clean masses.
- Bikita, Zimbabwe: considerable material mined for lithium content.
- Karibib, Namibia: colorless, transparent, and pinkish material.
- Afghanistan; Myanmar; Russia.
“Petalite,” San Piero in Campo, Elba Island, Livorno Province, Tuscany, Italy. © Rob Lavinsky, www.iRocks.com. Used with permission.
Stone Sizes
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.
- Smithsonian Institution (Washington, D.C.): 55 (colorless, Namibia): 48.3, 45.9, 26.6 (colorless, Brazil).
- Devonian Group (Calgary, Alberta, Canada): 14.8 (colorless. Australia).
- Private Collection: 48.25 (colorless).
Care
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.
