igneous
River Stone (likely Basalt or Gabro)
Mafic Igneous Rock
Hardness: 6-7 Mohs; Color: dark grey to black; Luster: dull; Crystal Structure: fine-grained (aphanitic); Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 Mohs
- Color
- dark grey to black
- Luster
- dull
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: dark grey to black; Luster: dull; Crystal Structure: fine-grained (aphanitic); Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the cooling of magnesium and iron-rich lava or magma. This specific rounded shape is the result of fluvial erosion (water wear) over thousands of years in a river or coastal environment.
Uses & applications
Used in landscaping, construction aggregate, aquarium decoration, and as 'worry stones' or for lithotherapy in spiritual practices.
Geological facts
Dark river stones like this are often composed of basalt, which is the most common rock type in the Earth's crust and makes up most of the ocean floor.
Field identification & locations
Identify in the field by its high density, dark color, and smooth, rounded surface from water tumbling. Found globally in riverbeds and beaches.
