Faceted xonotlite (about 2 carats): Laghi di Posina, Vicenza, Italy. Photo © Joel E. Arem, PhD, FGA. Used with permission.
Xonotlite is strong and can take a good polish. However, these gems are extremely rare, both as a species and cut specimens.
Xonotlite Information
| Data | Value |
|---|---|
| Name | Xonotlite |
| Crystallography | Monoclinic: crystals acicular; usually massive, fibrous, or compact. |
| Refractive Index | 1.583-1.593 |
| Colors | Chalky white to colorless, pink, light to medium gray. |
| Luster | Greasy; pearly; dull vitreous. |
| Hardness | 6 |
| Fracture | Splintery |
| Specific Gravity | 2.71 |
| Birefringence | 0.010 |
| Cleavage | Good in one direction |
| Luminescence | None reported. |
| Luminescence Present | No |
| Transparency | Transparent to translucent. |
| Absorption Spectrum | None. |
| Formula | Ca6Si6O17(OH)2 |
| Pleochroism | None. |
| Optics | a = 1.583; β = 1.583; γ = 1.593. Biaxial (+). |
| Optic Sign | Biaxial + |
| Etymology | After the type locality, Tetela de Xonotla, Mexico. |
| Occurrence | Typically as veinlets in serpentine or in contact zones. |
“Like a fly trapped in amber,” notes Rob Lavinsky, an ivory-colored xonotlite sphere lies within a layer of selenite. Other xonotlites and a red inesite appear on the surface. Xonotlites, selenite, and inesite, 4.8 x 4.2 x 2.2 cm, Wessel’s Mine, Kalahari Manganese Fields, South Africa. © Rob Lavinsky, www.iRocks.com. Used with permission.
Comments
Lapidaries have cut translucent (not truly transparent) faceted stones up to several carats in size from Italian material.
Synthetics
Researchers have synthesized xonotlite via the hydrothermal method. The synthetic material has been used in powder form for industrial purposes, such as absorption, insulation, and pigment extension. However, no jewelry use for this material is known.
Although xonotlite crystals can take acicular (needle-like) forms, like these specimens from Vicenza, Veneto, Italy, this material usually occurs as fibrous masses. Researchers who synthesize this mineral take particular interest in this fibrous property. Photo by Aangelo. Licensed under CC By-SA 3.0.
Enhancements
None known.
Sources
Mexico and the Vicenza region of Italy have produced gem-quality, facetable material.
- Tetela de Xonotla, Mexico.
- Laghi di Posina, Vicenza, Italy.
Emerald-cut xonotlite (about 2 carats): Laghi di Posina, Vicenza, Italy. Photo © Joel E. Arem, PhD, FGA. Used with permission.
Other notable sources include the following:
- United States: California; Michigan; Puerto Rico; Virginia.
- Canada; Japan; South Africa.
Care
Despite a mid-range hardness (6), xonotlites have greater resistance to blows than many jewelry gemstones. They have a “tough” tenacity, while most gemstones only rank as “brittle.” Nevertheless, you’re more likely to find these stones in mineral collections than in jewelry collections. Consult our gemstone jewelry cleaning guide for care recommendations.
The “broken” sphere of one of the xonotlite crystals in this specimen shows how this gem’s acicular crystal formations create these spherical aggregates. Xonotlites, Wessel’s Mine, Hotazel, Kalahari manganese fields, Northern Cape Province, South Africa. © Rob Lavinsky, www.iRocks.com. Used with permission.
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