Serpentine (Serpentinite)

Hardness: 3-6 (Mohs scale), Color: varying shades of green with mottling, Luster: waxy to greasy, Crystal structure: monoclinic, Cleavage: poor, Specific gravity: 2.5-2.6

Formed through serpentinization, which is the hydration of ultramafic rocks (like peridotite) from the Earth's mantle at low temperatures. Common in ophiolite sequences and subduction zones.

Used as an ornamental stone for carvings (like the shown mushroom), architectural facades, and occasionally as a source of magnesium. Historically used for asbestos, though modern commercial varieties are usually non-fibrous.

Serpentine is the official state rock of California. Its name is derived from the Latin 'serpentinus,' meaning 'resembling a serpent' due to its greenish, mottled texture that looks like snake skin.

Identify by its greasy feel, green color ranging from olive to blackish, and relative softness compared to nephrite jade. Often found in mountainous regions where oceanic crust has been uplifted.