igneous
Porphyritic Igneous Rock / Basalt or Andesite Xenolith in Granite or Quartzite
Silicate rock with contrasting xenolith/inclusion
Hardness: 6-7 on Mohs scale (due to quartz/silicate matrix), Color: White/grey matrix with dark grey to black contrasting inclusion, Luster: Vitreous to dull, Crystal structure: Cryptocrystalline to fine-grained, Specific gravity: 2.6-2.9
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Physical properties
Hardness: 6-7 on Mohs scale (due to quartz/silicate matrix), Color: White/grey matrix with dark grey to black contrasting inclusion, Luster: Vitreous to dull, Crystal structure: Cryptocrystalline to fine-grained, Specific gravity: 2.6-2.9
Formation & geological history
Formed via magmatic processes where an older rock fragment (xenolith) was incorporated into a cooling magma body, later exposed and weathered into a rounded pebble by water action.
Uses & applications
Used primarily as decorative landscape gravel, road aggregate, or educational specimens for studying geological inclusions.
Geological facts
This specimen displays a striking visual contrast where a dark mafic inclusion is embedded within a lighter felsic rock matrix, representing a snapshot of magmatic assimilation and mixing.
Field identification & locations
Can be identified by its water-worn, smooth pebble shape with distinct color-contrasting patches. Commonly found in riverbeds, glacial tills, and coastal beaches worldwide.
