igneous
Diabase (also known as Dolerite)
Diabase
Hardness: 6-7 on Mohs scale; Color: dark grey to black with light brown weathering; Luster: dull to sub-metallic; Crystal structure: fine to medium grained ophitic texture; Cleavage: poor; Specific gravity: 2.7-3.3
- Hardness
- 6-7 on Mohs scale
- Color
- dark grey to black with light brown weathering
- Luster
- dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; Color: dark grey to black with light brown weathering; Luster: dull to sub-metallic; Crystal structure: fine to medium grained ophitic texture; Cleavage: poor; Specific gravity: 2.7-3.3
Formation & geological history
Formed from the shallow-level cooling of mafic magma, often occurring in sills or dikes. This specimen shows significant rounding due to fluvial (river) or glacial transport.
Uses & applications
Used primarily as crushed stone for construction, road aggregate, and railroad ballast monument stone (black granite trade name).
Geological facts
Highly durable and dense, diabase makes up the famous Palisades Sill along the Hudson River. It is chemically similar to basalt but has a coarser grain size due to slower cooling underground.
Field identification & locations
Identify in the field by its high density, dark interior color, and typical brown weathered 'rind'. Found globally in areas of volcanic activity or ancient rifting.
