igneous
Amygdaloidal Basalt
Amygdaloidal Basalt
Hardness: 6-7 (groundmass); Color: Dark brown or black base with white/pink almond-shaped inclusions; Luster: Pearly to vitreous inclusions in a dull groundmass; Porphyritic/Vesicular texture.
- Hardness
- 6-7 (groundmass)
- Luster
- Pearly to vitreous inclusions in a dull groundmass
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Physical properties
Hardness: 6-7 (groundmass); Color: Dark brown or black base with white/pink almond-shaped inclusions; Luster: Pearly to vitreous inclusions in a dull groundmass; Porphyritic/Vesicular texture.
Formation & geological history
Formed from volcanic lava flows where gas bubbles (vesicles) were later filled with secondary minerals like quartz, calcite, or zeolites through groundwater infiltration long after solidification.
Uses & applications
Used primarily as decorative garden stones, in lapidary work for cabochons, and as a geological teaching specimen.
Geological facts
The term 'amygdule' comes from the Greek word 'amygdala', meaning almond, referring to the shape of the mineral fillings. This specifically looks like 'Rice Rock' or 'Peanut Obsidian' texture common in certain volcanic regions.
Field identification & locations
Look for a dark, dense volcanic matrix containing distinct, oval-shaped light-colored mineral pockets. Commonly found in the Lake Superior region of the US and other ancient volcanic terrains.
