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 April 7, 2026More igneous →

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Physical properties

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.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral