metamorphic
Soapstone (Talc-Schist)
Steatite (composed primarily of Talc: Mg3Si4O10(OH)2)
Hardness: 1.0–2.5 Mohs (can be scratched with a fingernail); Color: white to light green/grey; Luster: Pearly to greasy; Crystal Structure: Monoclinic; Cleavage: Basal; Specific Gravity: 2.7–2.8.
- Hardness
- 1
- Color
- white to light green/grey
- Luster
- Pearly to greasy
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Physical properties
Hardness: 1.0–2.5 Mohs (can be scratched with a fingernail); Color: white to light green/grey; Luster: Pearly to greasy; Crystal Structure: Monoclinic; Cleavage: Basal; Specific Gravity: 2.7–2.8.
Formation & geological history
Formed through the regional metamorphism of ultramafic rocks (like peridotite) or by hydrothermal alteration of dolostone. It occurs in areas where tectonic plates subduct, subjecting rocks to high pressure and low heat.
Uses & applications
Used in ornamental carving (as seen in the provided image), countertops, fireplace surrounds, electrical insulators, and traditionally for cooking pots due to its heat-retention properties.
Geological facts
Because of its high talc content, soapstone feels 'soapy' or greasy to the touch. This specific piece is an example of an engraved/scrimshaw-style decorative plaque set in a metal brooch, likely originating from East Asian folk art traditions.
Field identification & locations
Identify in the field by its extreme softness and characteristic 'greasy' feel. It is commonly found in metamorphic belts in Brazil, India, China, and the Appalachian mountains in the USA.
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