By Ji-Elle (Own work) [Public domain], via Wikimedia Commons
Talc
An overview on Talc Jewelry and Gemstones. Covers details and essential information on the physical properties and characteristics of Talc gemstones.
Talc Information
| Data | Value |
|---|---|
| Name | Talc |
| Varieties | Steatite |
| Colors | Pale green, dark green, greenish gray, white, gray, silvery white, brownish. Colors are due to impurities. |
| Stone Sizes | Steatite and soapstone are known in massive pieces that will yield large carvings, up to several pounds. |
| Formula | Mg3Si4O10(OH)2. |
| Fracture | Fibrous, micaceous |
| Hardness | 1 |
| Cleavage | Perfect 1 direction |
| Crystallography | Monoclinic, triclinic. Tabular crystals up to 1 cm; usually massive, foliated, fine grained, compact. |
| Refractive Index | 1.539-1.600 |
| Birefringence | Monoclinic: 0.050. Triclinic: 0.039. |
| Luminescence | Usually none. Some is pinkish in LW (Silver Kale, California). |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long |
| Absorption Spectrum | Not diagnostic. |
| Optics | Monoclinic: a = 1.539-1.550; β = 1.589-1.594; γ = 1.589-1.600. Triclinic: a = 1.545; β = 1.584; γ = 1.584. Biaxial (-), 2V=30° in monoclinic. Shadow edge at 1.54. |
| Optic Sign | Biaxial - |
| Luster | Greasy, pearly, dull. |
| Specific Gravity | 2.20-2.83 |
| Transparency | Translucent to opaque. |
TALC (=SOAPSTONE =STEATITE)
Optics: Monoclinic: a=1.539—1.550; β=1.589—1.594; γ= 1.589—l.600.
Triclinic: a= 1.545; β=1.584; γ= 1.584.
Biaxial {—), 2V=30° in monoclinic.
Shadow edge at 1.54.
Occurrence: In hydrothermally altered ultrabasic rocks and thermally altered siliceous dolomites. Worldwide occurrence, sometimes in large beds, often associated with serpentines.
Many localities in the United States, especially Vermont, New Hampshire, Massachusetts, Virginia, North Carolina, Georgia, California.
Lake Nyasa, Central Africa; India: China.” Australia; Zimbabwe; Canada: USSR.
Egypt: ancient deposit.
Comments: Steatite may be slightly harder than talc, due to impurities. Talc itself is often pseudomorphous after other minerals. Massive talc is easy to carve and is widely used for this purpose.
Talc has a greasy feel.
Name: Talc is from the Arabic word talk or talq, the name of the mineral. Steatite is from the Latin steatis, a type of stone, derived from the Greek word steatos, meaning fat.
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