Porphyritic Basalt (Chinese Writing Stone or Flower Stone)

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Black or dark grey groundmass with white, cream, or light green crystals; Luster: Dull to sub-vitreous; Crystal Structure: Aphanitic matrix with large phenocrysts (usually plagioclase feldspar); Cleavage: None for the rock, perfect for feldspar inclusions.

Formation & Geological History

Formed through a two-stage cooling process of volcanic magma. The large crystals (phenocrysts) formed slowly underground, while the surrounding dark matrix cooled quickly after eruption or shallow intrusion. Common in volcanic zones of the Pacific Northwest and Asia.

Uses & Applications

Used primarily for ornamental purposes, landscaping, as a lapidary material for jewelry (cabochons), and as a decorative collector's specimen.

Geological Facts

Also known as 'Chinese Writing Stone' or 'Flower Stone' in the lapidary community because the random patterns of the light feldspar crystals can resemble calligraphy or flower petals.

Field Identification & Locations

Identify in the field by looking for a fine-grained, dark green or black heavy rock containing distinct, lighter-colored rectangular or star-shaped crystals. Often found as water-worn pebbles in riverbeds and on beaches near volcanic regions.

Identified on: 4/15/2026

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