metamorphic
Serpentinite
Serpentinite (composed primarily of minerals in the serpentine group: (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4)
Hardness: 3-6 on Mohs scale; Color: typically mottled shades of green, yellow, and black; Luster: waxy to greasy; Crystal structure: monoclinic; Cleavage: poor; Specific gravity: approx 2.5-2.6.
- Hardness
- 3-6 on Mohs scale
- Color
- typically mottled shades of green, yellow, and black
- Luster
- waxy to greasy
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Physical properties
Hardness: 3-6 on Mohs scale; Color: typically mottled shades of green, yellow, and black; Luster: waxy to greasy; Crystal structure: monoclinic; Cleavage: poor; Specific gravity: approx 2.5-2.6.
Formation & geological history
Formed by the low-temperature metamorphic alteration of ultramafic rocks (like peridotite or pyroxenite) from the Earth's mantle through a process called serpentinization, usually at tectonic plate boundaries. The location provided (São Paulo region, Brazil) contains Proterozoic metamorphic belts where such rocks are geologically plausible.
Uses & applications
Used as decorative building stone (often called green marble), in jewelry and carvings (cabochons), and historically as a source of asbestos. High-quality specimens are popular for mineral collecting.
Geological facts
Serpentinite is the state rock of California. It often creates unique soil conditions (serpentine soils) that are toxic to many plants but host rare, endemic species. It is also significant in carbon sequestration research.
Field identification & locations
Identified by its distinctive 'snakeskin' appearance, green-mottled color, and waxy feel. It is relatively soft and can often be scratched with a copper coin or steel blade. Commonly found in ophiolite complexes.
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