igneous
Chinese Writing Stone
Porphyritic Basalt or Andesite with Feldspar phenocrysts (likely Orthoclase or Plagioclase)
Hardness: 5.5 to 6; Color: black to dark greenish-black matrix with white or creamy-yellow rectangular inclusions; Luster: dull to vitreous; Structure: porphyritic
- Hardness
- 5
- Luster
- dull to vitreous
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Physical properties
Hardness: 5.5 to 6; Color: black to dark greenish-black matrix with white or creamy-yellow rectangular inclusions; Luster: dull to vitreous; Structure: porphyritic
Formation & geological history
Formed from volcanic magma that cooled in two stages: slow cooling at depth allowed the large feldspar crystals to grow, followed by rapid cooling upon eruption which created the fine-grained dark matrix. Specimens are primarily from the Yangtze River valley, China.
Uses & applications
Decorative items, jewelry (cabochons), talismans, and display pieces for collectors due to its unique aesthetic.
Geological facts
The name comes from the white needle-like crystals that resemble Chinese calligraphy or characters. It is also known as Porphyry. Often confused with 'Chrysanthemum Stone,' which is a sedimentary stone with calcite/celestite crystals.
Field identification & locations
To identify in the field, look for the 'writing' pattern of light bladed crystals against a dark, basaltic groundmass. Most authentic specimens come from China or various California (USA) locales.
