igneous
Diabase (Dolerite)
Mafic Intrusive Igneous Rock
Hardness 6-7, color dark grey to black with salt-and-pepper texture, dull to sub-metallic luster, fine-to-medium grained crystalline structure, specific gravity 2.7-3.3
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Physical properties
Hardness 6-7, color dark grey to black with salt-and-pepper texture, dull to sub-metallic luster, fine-to-medium grained crystalline structure, specific gravity 2.7-3.3
Formation & geological history
Formed from the rapid cooling of basaltic magma within shallow crustal intrusions such as sills and dikes.
Uses & applications
Crushed stone for road beds, railroad ballast, building foundations, and sometimes used as dimension stone for monuments.
Geological facts
Diabase is chemically identical to basalt but has a larger grain size due to cooling underground rather than on the surface.
Field identification & locations
Identify by its interlocking crystal 'ophitic' texture under a lens and its high density; commonly found in rift basins and volcanic regions.
