igneous
Peridotite Nodules in Basalt (Xenolith)
Ultramafic Xenolith (Olivine-rich Peridotite in Basalt)
Hardness: 6.5 to 7 on Mohs scale (for olivine/pyroxene interior); Color: Olive-green to bluish-grey core with a rusty brownish-tan weathered outer rind; Luster: Vitreous to dull granular; Structure: Phaneritic, coarse-grained crystalline aggregate embedded in fine-grained igneous rock matrix.
- Hardness
- 6
- Luster
- Vitreous to dull granular
Identified More igneous →
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Physical properties
Hardness: 6.5 to 7 on Mohs scale (for olivine/pyroxene interior); Color: Olive-green to bluish-grey core with a rusty brownish-tan weathered outer rind; Luster: Vitreous to dull granular; Structure: Phaneritic, coarse-grained crystalline aggregate embedded in fine-grained igneous rock matrix.
Formation & geological history
Formed deep within the Earth's upper mantle at high pressures and temperatures. Mantle material is caught up and carried upward as fragments (xenoliths) by rapidly ascending basaltic magma during volcanic eruptions.
Uses & applications
Primarily of scientific interest for studying Earth's upper mantle composition. Highly prized by geological collectors, educational institutions, and rockhounding enthusiasts.
Geological facts
Xenoliths mean 'foreign rocks' in Greek. These mantle xenoliths represent actual pieces of the Earth's upper mantle brought up from depths of 30 to over 100 kilometers below the surface.
Field identification & locations
Identified by a distinct granular green-to-grey interior encased in a dark basaltic or weathered iron-oxide crust. Commonly found in volcanic regions, alkali basalt fields, and volcanic pipes globally.
