igneous
Porphyritic Basalt (Chinese Writing Stone)
Porphyritic Basalt with Feldspar Phenocrysts
Hardness: 6-7 (Mohs); Color: Dark grey to black groundmass with white/pale grey laths; Luster: Dull to sub-vitreous; Crystal structure: Porphyritic (fine-grained matrix with larger visible crystals); Cleavage: Indistinct; Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 (Mohs)
- Color
- Dark grey to black groundmass with white/pale grey laths
- Luster
- Dull to sub-vitreous
Identified More igneous →
Explore Porphyritic Basalt (Chinese Writing Stone) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs); Color: Dark grey to black groundmass with white/pale grey laths; Luster: Dull to sub-vitreous; Crystal structure: Porphyritic (fine-grained matrix with larger visible crystals); Cleavage: Indistinct; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from volcanic lava cooling in two stages: slow cooling at depth allowed large crystals (phenocrysts) to form, followed by rapid cooling at the surface forming the fine-grained matrix. Found in Cenozoic volcanic regions.
Uses & applications
Primarily used as a decorative stone, for lapidary work (cabochons), and in ornamental carvings or architectural accents.
Geological facts
The name 'Chinese Writing Stone' (or Basalt) comes from the needle-like crystals of feldspar that resemble traditional Chinese characters or calligraphy marks.
Field identification & locations
Identify by the distinct 'matchstick' or calligraphic pattern of light crystals against a dark background. Commonly found in California (USA), Canada, and Asia near anciennes volcanic flows.
