igneous
Alkali Basalt with iron oxidation
Mafic Volcanic Rock (Fe-bearing Basalt)
Hardness: 6.0; Color: Dark grey to charcoal base with reddish-brown (limonite/hematite) oxidation spots; Luster: Dull/Earthy; Crystal Structure: Fine-grained/Aphanitic; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Luster
- Dull/Earthy
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.0; Color: Dark grey to charcoal base with reddish-brown (limonite/hematite) oxidation spots; Luster: Dull/Earthy; Crystal Structure: Fine-grained/Aphanitic; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The orange-red spotting is caused by the chemical weathering and oxidation of iron-bearing minerals (like olivine or pyroxene) within the rock matrix over time.
Uses & applications
Used primarily in construction as crushed stone, road base, or decorative garden stones. Due to its smooth, river-worn shape, it is often used in landscaping or as a pocket stone.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The 'rusty' appearance on this specimen indicates it has been exposed to oxygen and water for a significant period.
Field identification & locations
Identify in the field by its high density (heavy for its size), dark interior, and the presence of rust-colored oxidation pods. Commonly found in volcanic regions or in riverbeds where it has been smoothed by water action.
