Porphyry (Flower Stone)

Physical Properties

Hardness: 6-7 Mohs; Color: Dark grey/green groundmass with white/cream laths; Luster: Dull to sub-vitreous; Crystal structure: Porphyritic (fine-grained matrix with large crystals); Cleavage: Indistinct; Specific Gravity: 2.5-3.0.

Formation & Geological History

Formed from molten rock (magma) that cooled in two stages: initially slow cooling deep underground to form large crystals (phenocrysts), followed by rapid cooling upon eruption or intrusion to form the fine-grained matrix.

Uses & Applications

Used primarily as decorative stone, garden accents, and by collectors. In some regions, it is polished for use in jewelry or as 'cabinet specimens'.

Geological Facts

Commonly known as 'Flower Stone' or 'Chrysanthemum Stone' when found in riverbeds (though distinct from the true mineral-based Chrysanthemum Stone). These patterns are caused by the interlocking of plagioclase feldspar crystals.

Field Identification & Locations

Identify by looking for distinct, light-colored 'flower' or 'lath' shapes embedded in a dark, hard matrix. Often found in glacial till, riverbeds, and volcanic regions of the Pacific Northwest and Japan.

Identified on: 4/15/2026

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