igneous
Amygdaloidal Basalt with Quartz
Basalt with Secondary Mineral Infilling
Hardness: 6 (basalt matrix), 7 (quartz inclusions). Color: Dark brown/black matrix with white and green-yellow streaks. Luster: Dull to waxy. Structure: Fine-grained/aphanitic matrix with irregular crystal pockets.
- Hardness
- 6 (basalt matrix), 7 (quartz inclusions)
- Color
- Dark brown/black matrix with white and green-yellow streaks
- Luster
- Dull to waxy
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Physical properties
Hardness: 6 (basalt matrix), 7 (quartz inclusions). Color: Dark brown/black matrix with white and green-yellow streaks. Luster: Dull to waxy. Structure: Fine-grained/aphanitic matrix with irregular crystal pockets.
Formation & geological history
Formed from the rapid cooling of basaltic lava. The white and yellowish sections are quartz or epidote that filled gas bubbles (vesicles) in the cooling lava through hydrothermal deposition.
Uses & applications
Primarily used as a lapidary material for decorative stones, river rock landscaping, or as a teaching specimen for volcanic processes.
Geological facts
The term 'amygdule' comes from the Greek word 'amygdala', meaning almond, referring to the almond-shaped holes filled by minerals. This specific sample shows significant river tumbling, smoothing its exterior.
Field identification & locations
Commonly found in volcanic regions, particularly ancient lava flows near riverbeds or glacial deposits. Identify by its heavy weight and the contrast between the dark matrix and bright mineral veins.
