metamorphic
Serpentine (likely serpentinite)
Serpentine-group minerals, chiefly antigorite/lizardite; commonly with magnetite and carbonate
AI-generated identification · may be incorrectPale green to cream with black-green veining and mottled patches; waxy to dull luster; fine-grained and massive, lacking visible crystal faces. Mohs hardness about 2.5–4, specific gravity roughly 2.5–2.6; generally poor cleavage. The polished/tumbled surface and surrounding stones indicate a prepared specimen.
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Physical properties
Pale green to cream with black-green veining and mottled patches; waxy to dull luster; fine-grained and massive, lacking visible crystal faces. Mohs hardness about 2.5–4, specific gravity roughly 2.5–2.6; generally poor cleavage. The polished/tumbled surface and surrounding stones indicate a prepared specimen.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during metamorphism, often along faults or oceanic crust. Serpentinization commonly occurred from the Precambrian to Cenozoic; precise age cannot be determined visually.
Uses & applications
Used as decorative stone, carvings, countertops, and ornamental tumbled material; historically used as a low-grade architectural stone. Valuable specimens are mainly collectible rather than gemstone-grade.
Geological facts
Black veining may be magnetite, chromite, or other associated minerals. Serpentine is often confused with jade, but it is softer and usually less dense and tougher.
Field identification & locations
Identify by its green/cream mottling, greasy or waxy feel, low hardness, and dark vein network; a steel knife commonly scratches it. Serpentinite is plausible in northeastern Mexico, although the exact locality cannot be confirmed from the image.
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