Serpentine

Serpentine is a group of minerals that form through the hydration and metamorphism of ultramafic rocks - iron and magnesium-rich rocks from the Earth's mantle. When oceanic crust is thrust onto continental margins (a process called obduction), the mantle rocks are exposed to water and undergo serpentinization - a chemical reaction where olivine and pyroxene minerals absorb water and transform into serpentine.

This process is geologically significant: serpentinization releases hydrogen gas and heat, and may support deep subsurface microbial life. Some scientists have proposed that serpentinization on early Earth could have provided the chemical energy for the origin of life.

Serpentine ranges from translucent lime green (antigorite and chrysotile varieties) to dark, waxy olive green (lizardite). The name comes from the Latin 'serpentinus' meaning 'resembling a serpent' - the mottled green color and sometimes scaly texture reminded early mineralogists of snakeskin. Bowenite, the hardest and most translucent variety, is carved as a jade substitute in some traditions.

Serpentine is identified by its greasy to waxy luster, green color, low hardness (3-5 depending on variety), and association with ultramafic rocks. It feels soapy or slippery to the touch.

Distinguish from jade (much harder at 6-7, denser), green marble (fizzes in acid), and soapstone (even softer at 1-2). Serpentine is commonly mislabeled as 'new jade' in the crystal market - it's a completely different mineral. The waxy feel and low hardness are the quickest distinguishing tests.