Basalt
Rock
Also called Vesicular basalt, Amygdaloidal basalt, and Trap
About it
Dark, fine-grained lava rock, often with gas holes (vesicles) that may be filled with agate, zeolites, or copper. The commonest rock of the ocean floor; forms the Columbia River and Deccan plateaus and the columns of the Giant's Causeway.
- Type
- Rock (igneous)
- Group
- Igneous (volcanic)
- Specific gravity
- 2.7–3.1
- Lustre
- dull
- Colours
- black, dark grey, reddish brown when weathered
- Transparency
- opaque
- Magnetic
- Weakly
Typical values: real specimens vary. For more, see mindat.org.