igneous
Basalt with Granite Inclusions (Xenolith)
Mafic Igneous Rock (Basalt) with Felsic Igneous Inclusion (Granite)
Hardness: 6-7 (Basalt) and 6-6.5 (Granite). Color: Dark gray/black matrix with white, cream, and pinkish granular inclusions. Luster: Dull/earthy matrix with vitreous inclusions. Crystal structure: Fine-grained aphanitic matrix containing phaneritic crystalline inclusions.
- Hardness
- 6-7 (Basalt) and 6-6
- Luster
- Dull/earthy matrix with vitreous inclusions
Identified More igneous →
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Physical properties
Hardness: 6-7 (Basalt) and 6-6.5 (Granite). Color: Dark gray/black matrix with white, cream, and pinkish granular inclusions. Luster: Dull/earthy matrix with vitreous inclusions. Crystal structure: Fine-grained aphanitic matrix containing phaneritic crystalline inclusions.
Formation & geological history
Formed when a cooling mafic lava flow (basalt) picked up and incorporated fragments of pre-existing felsic crustal rock (granite). The granite fragment remained solid as a 'xenolith' within the hotter basaltic magma.
Uses & applications
Primarily used as a teaching specimen for geological processes (inclusions and intrusive relationships); also used in construction aggregate and road base.
Geological facts
The word 'xenolith' comes from the Greek words for 'foreign rock.' These specimens provide a glimpse into the composition of the Earth's crust beneath the surface where the lava erupted.
Field identification & locations
Look for a distinct 'mottled' appearance where large, light-colored crystals are embedded in a smooth, dark, fine-grained rock. Commonly found in volcanic fields, glacial till, and riverbeds in tectonic regions.
