igneous
Diabase
Diabase (Dolerite)
Hardness: 6-7 on Mohs scale; Color: dark grey to black, often with greenish tint; Luster: sub-vitreous to dull; Crystal structure: fine to medium grained with ophitic texture; Cleavage: poor; Specific gravity: 2.7-3.3
- Hardness
- 6-7 on Mohs scale
- Color
- dark grey to black, often with greenish tint
- Luster
- sub-vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: dark grey to black, often with greenish tint; Luster: sub-vitreous to dull; Crystal structure: fine to medium grained with ophitic texture; Cleavage: poor; Specific gravity: 2.7-3.3
Formation & geological history
Formed through the cooling of mafic magma within shallow dikes or sills. It is chemically similar to basalt but has a coarser grain size due to slower cooling beneath the surface.
Uses & applications
Predominantly used as crushed stone for construction, road beds, and railroad ballast. Fine-grained varieties are sometimes used for headstones or decorative building facades known as black granite.
Geological facts
Diabase is the primary rock of the famous Palisades Sill along the Hudson River. It is frequently associated with the breakup of supercontinents like Pangea, appearing in massive rift-related dike swarms.
Field identification & locations
Identify in the field by its dark color, notable weight/density, and the interlocking 'sugary' texture of light plagioclase and dark pyroxene crystals. Found globally in volcanic provinces.
