Serpentine

Physical Properties

Hardness: 3 to 6 on Mohs scale; Color: Dark green to black, often mottled; Luster: Waxy to greasy; Crystal Structure: Monoclinic; Cleavage: Poor/basal; Specific Gravity: 2.5 to 2.6.

Formation & Geological History

Formed through serpentinization, a low-temperature metamorphic process where ultramafic rocks from the Earth's mantle (like peridotite) are hydrated by seawater or hydrothermal fluids. Common in subduction zones and ophiolite complexes.

Uses & Applications

Used as an architectural decorative stone, in carvings, figurines, and sometimes as a minor gemstone looks-alike for jade. Historically used as a source of asbestos and in industrial magnesium production.

Geological Facts

Serpentinite is the official state rock of California. Its name is derived from its resemblance to the skin of a serpent, both in color and texture. It often contains inclusions of magnetite, which can make it slightly magnetic.

Field Identification & Locations

Identify in the field by its distinctive waxy 'soapy' feel and dark green, mottled appearance. It is commonly found in mountain belts, such as the Appalachian Mountains or the Coast Ranges of California and Oregon. Collectors should check for softness (it can usually be scratched with a steel knife).

Identified on: 4/19/2026

Mode: Standard