igneous
Amygdaloidal Basalt
Amygdaloidal Basalt containing Zeolite and Calcite inclusions
Hardness: 5-7 (matrix) / 3-5 (inclusions). Color: Dark gray to black matrix with white or light green spots. Luster: Dull/earthy matrix, vitreous/pearly inclusions. Texture: Vesicular or amygdaloidal.
- Hardness
- 5-7 (matrix) / 3-5 (inclusions)
- Color
- Dark gray to black matrix with white or light green spots
- Luster
- Dull/earthy matrix, vitreous/pearly inclusions
Identified More igneous →
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Physical properties
Hardness: 5-7 (matrix) / 3-5 (inclusions). Color: Dark gray to black matrix with white or light green spots. Luster: Dull/earthy matrix, vitreous/pearly inclusions. Texture: Vesicular or amygdaloidal.
Formation & geological history
Formed from cooled volcanic lava (Basalt). The 'amygdules' (the white spots) formed when gas bubbles (vesicles) were later filled with secondary minerals like calcites, zeolites, or quartz through hydrothermal fluid activity.
Uses & applications
Used primarily in road construction and as aggregate. Specific amygdaloidal specimens are valued by geological collectors for their mineral diversity.
Geological facts
The word 'amygdule' comes from the Greek word 'amygdala', meaning almond, referring to the almond-shaped mineral fillings within the rock.
Field identification & locations
Identified by the dark, fine-grained volcanic matrix punctuated by rounded, lighter-colored mineral 'pockets'. Commonly found in volcanic rift zones like the Lake Superior region or the Deccan Traps.
