igneous
Amygdaloidal Basalt
Amygdaloidal Basalt
Hardness: 5-6 (matrix); Color: Dark brown to reddish-brown (oxidized) with white/cream inclusions; Luster: Dull/earthy matrix with vitreous inclusions; Structure: Vesicular/Amygdaloidal; Specific Gravity: 2.8-3.0
- Hardness
- 5-6 (matrix)
- Luster
- Dull/earthy matrix with vitreous inclusions
Identified More igneous →
Explore Amygdaloidal Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (matrix); Color: Dark brown to reddish-brown (oxidized) with white/cream inclusions; Luster: Dull/earthy matrix with vitreous inclusions; Structure: Vesicular/Amygdaloidal; Specific Gravity: 2.8-3.0
Formation & geological history
Formed from cooled volcanic lava where gas bubbles (vesicles) were later filled with secondary minerals like quartz, calcite, or zeolites through groundwater infiltration long after the initial eruption.
Uses & applications
Used primarily for geological study, landscaping, and as a decorative rock for collectors. In larger quantities, basalt is used for crushed stone in construction.
Geological facts
The word 'amygdule' comes from the Greek word for 'almond', referring to the almond-like shape of the mineral fillings in the rock. This specimen shows significant oxidation, giving it a rusty brown color.
Field identification & locations
Identify in the field by looking for a dark, heavy volcanic matrix containing distinct 'plugs' of lighter colored minerals. Commonly found in volcanic regions like the Lake Superior basin or Iceland.
