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.
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.
| 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.
Despite a mid-range hardness (6), which makes xonotlites somewhat vulnerable to scratches, these gems have greater resistance to blows than most jewelry stones. 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.
Lapidaries have cut translucent (not truly transparent) faceted stones up to several carats in size from Italian material.
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.
There are no known treatments or enhancements for xonotlites.
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.
Mexico and the Vicenza region of Italy have produced gem-quality, facetable material.
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:
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. Wessel’s Mine, Hotazel, Kalahari manganese fields, Northern Cape Province, South Africa. © Rob Lavinsky, www.iRocks.com. Used with permission.
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