igneous
Diabase (Greenstone)
Diabase or Dolerite
Hardness: 6-7 (Mohs scale); Color: dark gray, greenish-black, or mottled; Luster: dull to sub-metallic; Crystal structure: phaneritic to aphanitic with ophitic texture; Specific gravity: approx. 3.0
- Hardness
- 6-7 (Mohs scale)
- Color
- dark gray, greenish-black, or mottled
- Luster
- dull to sub-metallic
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs scale); Color: dark gray, greenish-black, or mottled; Luster: dull to sub-metallic; Crystal structure: phaneritic to aphanitic with ophitic texture; Specific gravity: approx. 3.0
Formation & geological history
Formed through the cooling of mafic magma in shallow intrusive bodies like dikes or sills. This specific specimen appears water-worn, suggesting a secondary transport process by a river or coastline.
Uses & applications
Used primarily as crushed stone for construction aggregates, road base, and railroad ballast. Exceptionally durable specimens are used for 'black granite' countertops or monuments.
Geological facts
Many of the inner stones at Stonehenge are diabase 'bluestones.' It is chemically similar to basalt but has a slightly larger crystal size due to cooling more slowly underground.
Field identification & locations
Identify by its heavy weight (high density), dark color, and fine-grained 'salt and pepper' appearance. Common in rift zones and oceanic crust settings.
