igneous
Porphyritic Basalt (likely Chinese Writing Stone)
Porphyritic Basalt / Plagioclase Feldspar in Basal Matrix
Hardness: 6-7 (Mohs scale); Color: Dark grey to black matrix with white or light-grey lath-like inclusions; Luster: Dull to sub-vitreous; Crystal Structure: Aphanitic matrix with large phenocrysts; Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 (Mohs scale)
- Luster
- Dull to sub-vitreous
Identified More igneous →
Explore Porphyritic Basalt (likely 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 scale); Color: Dark grey to black matrix with white or light-grey lath-like inclusions; Luster: Dull to sub-vitreous; Crystal Structure: Aphanitic matrix with large phenocrysts; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through rapid cooling of volcanic lava on the surface, where larger crystals (phenocrysts) had already begun to form slowly underground before being erupted and trapped in a fine-grained matrix. Often associated with Mesozoic volcanic activity.
Uses & applications
Used primarily as decorative stone, lapidary carvings, cabochons for jewelry, and as a unique collector's specimen due to its patterns.
Geological facts
Commonly nicknamed 'Chinese Writing Stone' because the randomly oriented, elongated feldspar crystals resemble traditional Chinese calligraphy. It is sometimes classified as a porphyry rather than just basalt.
Field identification & locations
Identify in the field by the distinct 'needle' or 'stick' patterns of lighter crystals against a dark, hard igneous background. Commonly found in California (USA), Canada, and Asia. Collectors look for high contrast between the 'letters' and the background.
