Serpentine-rich rock

Olive-green to yellow-brown, mottled and opaque with a waxy to dull luster; typically massive rather than visibly crystalline. Mohs hardness is about 2.5–4, with poor cleavage and specific gravity around 2.5–2.6.

Forms when ultramafic rocks such as peridotite undergo low-temperature hydrothermal metamorphism and hydration, commonly along tectonic plate boundaries. Serpentinite ranges from Precambrian to modern geological ages.

Used as decorative stone, carvings, countertops, and historically as a source of asbestos-bearing serpentine; attractive specimens are collected. Its value is generally modest unless unusually patterned or polished.

The yellow-green color and patchy, slick-looking texture are characteristic, but this small specimen could also contain epidote, chlorite, or other alteration minerals.

Common in ophiolites and subduction-zone mélanges, including California, Italy, New Zealand, and the Appalachians. A soft, green, waxy rock that may scratch with a steel knife supports identification; avoid cutting or abrading unknown material because some serpentinite contains chrysotile asbestos.