Serpentine

Hardness: 2.5-5.5 (Mohs); Color: Shades of green (pale to dark), yellow-green, brownish-green, blackish-green, often mottled or veined; Luster: Waxy to greasy, silky (chrysotile); Crystal structure: Monoclinic or triclinic, often massive to fibrous aggregates; Cleavage: Good in some varieties, none in others; Specific Gravity: 2.5-2.8

Formed by the metamorphism of ultramafic rocks (like peridotite and dunite) through a process called serpentinization. This occurs when these rocks are exposed to water and heat, typically at convergent plate boundaries or along major fault zones. The process involves hydration of olivine and pyroxene minerals into serpentine minerals. Geological age can vary widely depending on the original ultramafic rock and the timing of the metamorphic event, ranging from Precambrian to Cenozoic.

Industry: Used as an ornamental stone, building material (e.g., floor tiles, facing stone), and sometimes for heat-resistant materials. Jewelry: Carved into beads, cabochons, and ornamental objects. Collecting Value: Attractive specimens are sought after by mineral collectors, especially those with interesting colors or patterns.

The name 'serpentine' comes from the mottled green colors reminiscent of a serpent's skin. It is sometimes incorrectly referred to as 'new jade' or 'Korean jade' due to its similar appearance to true jade (jadeite and nephrite), but it is a distinct mineral group. Some varieties, particularly chrysotile, are fibrous and were historically used as asbestos due to their heat resistance and insulating properties. However, chrysotile asbestos is now recognized as a health hazard. Serpentinite rock formations can host economically important deposits of other minerals, including nickel, chromium, and talc.

Identification in the field: Look for its characteristic greasy or waxy luster, varying shades of green, and often mottled appearance. It may feel smooth or slightly soapy to the touch. Can be scratched with a knife (hardness typically below 6). Common locations: Found globally in areas that have experienced metamorphism of ultramafic rocks, including the Appalachian Mountains (USA), California (USA), Canada, Russia, Afghanistan, China, New Zealand, and various European countries. Tips for collectors: Be aware that some fibrous varieties may contain asbestos. Observe for variations in color and texture. Easily carved and polished.