igneous
Basalt with Quartz/Zeolite Inclusions
Porphyritic Basalt (SiO2 with Aluminosilicates)
Hardness: 5-7 on Mohs scale; Color: Black or dark grey groundmass with white/clear inclusions; Luster: Vitreous (crystals) to dull/earthy (matrix); Structure: Aphanitic to porphyritic; Cleavage: None to poor.
- Hardness
- 5-7 on Mohs scale
- Color
- Black or dark grey groundmass with white/clear inclusions
- Luster
- Vitreous (crystals) to dull/earthy (matrix)
Identified More igneous →
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Physical properties
Hardness: 5-7 on Mohs scale; Color: Black or dark grey groundmass with white/clear inclusions; Luster: Vitreous (crystals) to dull/earthy (matrix); Structure: Aphanitic to porphyritic; Cleavage: None to poor.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The white crystals represent minerals that grew earlier in the magma chamber or secondary minerals filling vesicles (gas bubbles) after the lava cooled.
Uses & applications
Primarily used in construction as aggregate or road base in its bulk form; smaller decorative pieces are used in aquarium gravel, landscaping, or as introductory collector specimens.
Geological facts
Basalt is the most common rock in the Earth's crust and makes up most of the ocean floor. The white inclusions in specimens like this one often provide a record of different cooling stages or later hydrothermal activity.
Field identification & locations
Identify by its dark, heavy fine-grained matrix and the high contrast of the white crystal inclusions. Commonly found in volcanic regions, coastal beaches near basaltic flows, and riverbeds. Collectors look for high contrast and clear crystal shapes.
