igneous
Basalt with Amygdales
Amygdaloidal Basalt
Hardness: 5-6 (Mohs); Color: Dark grey to charcoal with small white circular inclusions; Luster: Dull, earthy; Structure: Fine-grained aphanitic matrix with vesicle fillings; Cleavage: None.
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to charcoal with small white circular inclusions
- Luster
- Dull, earthy
Identified More igneous →
Explore Basalt with Amygdales in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to charcoal with small white circular inclusions; Luster: Dull, earthy; Structure: Fine-grained aphanitic matrix with vesicle fillings; Cleavage: None.
Formation & geological history
Formed from the rapid cooling of basaltic lava. The circular white spots (amygdales) are formed when gas bubbles (vesicles) in the cooling lava are later filled with secondary minerals like calcite, quartz, or zeolites through groundwater infiltration.
Uses & applications
Commonly used in construction as crushed stone, road base, or concrete aggregate. Large decorative specimens may be used in landscaping or small-scale mineral collecting.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. When the gas bubbles remain empty, the rock is called vesicular basalt; when they fill, it becomes amygdaloidal.
Field identification & locations
Can be identified by its dark, dense matrix and rounded, light-colored 'mineral pockets'. Found in volcanic regions globally, such as the Deccan Traps, Iceland, or the Pacific Northwest.
