Serpentinite (metamorphic rock)
California Serpentine
California Serpentine, officially designated as Serpentinite, is the state rock of California. It is a metamorphic rock derived from magnesium-rich igneous rocks (peridotite) from the Earth's mantle. Characterized by its distinctive blue-green, green, purple, or pink hues, often with slick surfaces and a greasy or scaly texture. It can also exhibit orange coloration due to oxidizing pyrite and chalcopyrite. Its relatively soft nature makes it easily carved.
- Origin
- California, USA
- Quarry
- Historically quarried in various locations across California, including San Luis Obispo, San Mateo, and the Sierra Nevada regions. Notable sites include Wolfard Quarry in Smith Hill and the Clear Creek, Idria serpentine body.
- Mohs hardness
- 2.5-3.5 (Serpentine group minerals). This indicates it is a relatively soft stone, easily scratched.
- Water absorption
- Serpentine contains approximately 15% H2O by weight. While not a direct water absorption percentage for dimension stone, its mineralogical composition indicates significant water content. Low porosity is generally associated with serpentinite, but specific absorption rates for dimension stone applications are not readily available. (For comparison, some studies mention water loss at shock pressures).
- ASTM spec
- ASTM C1526-19(2023)e1 Standard Specification for Serpentine Dimension Stone. Serpentinite is known for its high water content, which can be relevant in certain applications like neutron-radiation shielding.
- Installed price
- $20 - $60 (Based on general natural stone installation costs. Serpentine is often used for decorative purposes or smaller architectural elements, making direct comparisons to large slab installations difficult. General natural stone veneer can range from $35-$50/sq ft for material, with installation adding $20-$30/sq ft. Stacked stone walls can be $20-$60/sq ft installed).
- Slab price
- Not widely available for large architectural slabs. Smaller decorative slabs or raw material might be found on platforms like Etsy (e.g., raw serpentine slabs for around $6.49 for small pieces). Pricing would be highly variable depending on size, quality, and finish.
- Finishes
- Polished, carved, natural cleft, sawn. Its soft nature allows for intricate carving.
- Applications
- Decorative stone, carving, architectural elements, landscaping, countertops (less common due to softness), and historically in building construction.
- USA distributors
- Due to its status as the state rock and its unique properties, it is often distributed by specialized stone suppliers and landscape material companies within California. Specific large-scale distributors are not easily identified for dimension stone.
- Maintenance
- Relatively soft, so prone to scratching. Easily carved. Can be polished to a high sheen. Requires gentle cleaning. Due to its unique mineralogy, some serpentinites can have issues with heavy metals (e.g., chromium), which is more relevant for soil science than dimension stone maintenance.