Serpentine Group (Chrysotile and Antigorite) - Mg₃Si₂O₅(OH)₄

Habit: White, gray, yellow to green or brown to black. Minute crystals, typically platy, rarely elongated; commonly bladed or fibrous. Silky, greasy or vitreous luster; translucent to opaque. White streak.

Environment: Commonly replaces ultramafic rocks, pervasively or in crosscutting veinlets; also occurs as a replacement of siliceous dolostone along contacts with diabase sills.

Etymology: Named in 1834 from the Greek chrysos, meaning "gold," and tilos, meaning "fiber." The serpentine group describes a common group of minerals. Serpentine may refer to any of the 20 varieties belonging to this group; the main minerals are antigorite, chrysotile and lizardite.

Among the serpentine group, the chrysotile minerals are more likely to form serpentine asbestos. Asbestos was heavily used in the mid-20th century for fire-retardant coatings, pipe insulation and fireproof drywall, roofing and flooring, but its use was discontinued when its fibers were found to pose a health hazard.