metamorphic
Serpentinite (likely antigorite-rich)
Serpentinite; hydrated Mg-rich silicate minerals, chiefly antigorite (Mg3Si2O5(OH)4), with possible chrysotile/lizardite and magnetite
AI-generated identification · may be incorrectDark green to black, strongly fibrous or foliated with silky to waxy luster; typically Mohs 2.5–4, poor cleavage, variable specific gravity around 2.5–2.7. The parallel striations and mottled green matrix are characteristic of a sheared, veined serpentinite.
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Physical properties
Dark green to black, strongly fibrous or foliated with silky to waxy luster; typically Mohs 2.5–4, poor cleavage, variable specific gravity around 2.5–2.7. The parallel striations and mottled green matrix are characteristic of a sheared, veined serpentinite.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during low-temperature hydrothermal or subduction-related metamorphism. It commonly forms in ophiolites and mélange zones; exact age cannot be determined from the photograph.
Uses & applications
Used as decorative and ornamental stone, carvings, countertops, and historically as “green marble”; attractive pieces are collected. Avoid cutting or sanding unknown material because some serpentinite can contain fibrous chrysotile asbestos.
Geological facts
The pale patches may be carbonate or talc-rich veins, while the dark streaks can include magnetite and chromite. At approximately 15.2°N, 44.2°E, serpentinite is geologically plausible in Yemen’s ophiolitic and tectonic zones, though locality confirmation requires field tests.
Field identification & locations
Identify by its green-black color, waxy feel, fibrous/foliated texture, and relatively low hardness; it may be scratched by a steel knife. A streak, hardness, acid, and thin-section test would distinguish it from chlorite schist or altered gabbro.
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