Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Pyrophyllite resembles talc in many ways and is indistinguishable by eye from soapstone. Chemical tests are needed to distinguish them. North Carolina material is often used in carvings, as is the material from China known as agalmatolite.
| Data | Value |
|---|---|
| Name | Pyrophyllite |
| Colors | White, yellow, pale blue, grayish green, brownish green. |
| Crystallography | Monoclinic. Crystals tabular, often curved and deformed; foliated, radial, granular, compact. |
| Refractive Index | 1.534-1.601 |
| Luster | Pearly to dull, greasy. |
| Hardness | 1-2 |
| Specific Gravity | 2.65-2.90 |
| Birefringence | 0.050 |
| Cleavage | Perfect 1 direction |
| Stone Sizes | Cabochons and carvings are cut from massive material, any practical size. |
| Luminescence | Weak cream white in LW (China) — variety called agalmatolite. |
| Luminescence Present | Yes |
| Luminescence Type | Fluorescent, UV-Long |
| Transparency | Translucent to opaque. |
| Absorption Spectrum | Not diagnostic. |
| Formula |
Al2Si4O10(OH)2. |
| Optics |
a = 1.534-1.556; β = 1.586-1.589; γ = 1.596-1.601. Biaxial (-), 2V = 53-62°. Vague shadow edge on refractometer at about 1.6. |
| Optic Sign | Biaxial - |
Optics: a = 1.534—1.556; β= 1.586-1.589; γ= 1.596-1.601.
Biaxial (-), 2V = 53—62°.
Vague shadow edge on refractometer at about 1.6.
Occurrence: In schistose metamorphic rocks; also in hydrothermal veins with micas, quartz.
California; Arizona; Deep River, North Carolina; Pennsylvania; Georgia.
Minus Gerais, Brazil; Mexico; Sweden; Belgium;
Switzerland; Japan; USSR; Korea.
Transvaal, South Africa: so-called koranna stone, which is dark gray and is about 86% pyrophyllite; R.I. ~ 1.58, S.G. 2.72; also called South African Wonderstone.
Comments: Pyrophyllite resembles talc in many ways and is indistinguishable by eye from soapstone. Chemical tests are needed to distinguish them. North Carolina material is often used in carvings, as is the material from China known as agalmatolite.
Name: From the Greek words for fire and leaf because of the sheet-like nature and thermal properties of the mineral. Agalmatolile means figure stone, in allusion to its use in carvings.
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