igneous
Porphyritic Basalt (Leopard Palm Stone)
Porphyritic Mafic Volcanic Rock
Hardness: 6-7 on Mohs scale; Color: Dark grey or black groundmass with light off-white or cream phenocrysts; Luster: Dull to sub-vitreous; Structure: Porphyritic (fine-grained matrix with large visible crystals); Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Dark grey or black groundmass with light off-white or cream phenocrysts; Luster: Dull to sub-vitreous; Structure: Porphyritic (fine-grained matrix with large visible crystals); Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through two-stage cooling of magma. Large crystals (phenocrysts), typically plagioclase feldspar, form slowly deep underground, then the remaining melt is rapidly erupted as lava, cooling quickly to form the fine-grained matrix.
Uses & applications
Primarily used as decorative stones, pocket stones in the crystal healing community, or as geological teaching specimens. When found in large quantities, basalt is used in road construction and as aggregate.
Geological facts
This specific texture is often referred to as 'Leopard Skin' or 'Crowfoot' basalt depending on the shape of the crystals. Basalt is the most common rock type in the Earth's crust and covers most of the ocean floor.
Field identification & locations
Identifiable by the distinct contrast between the large, chunky white mineral inclusions and the darker, fine-grained background. Commonly found in volcanic regions like the Pacific Northwest of the US, Scotland, and India.
