silky lustre

mineralogy

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July 13, 2026

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In mineralogy, lustre describes the way a mineral's surface reflects light. Silky lustre specifically refers to a sheen resembling that of silk or satin. This type of lustre is characteristic of minerals with a fibrous structure, such as satin spar (a form of gypsum) and chrysotile asbestos. Chatoyance, or the "cat's-eye" effect, is a related phenomenon where a luminous band appears within a polished stone, also often exhibiting a silky lustre due to parallel fibers or inclusions.123

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mineral
Lustre
…milky quartz may exhibit this); silky, descriptive of the lustre of a skein of silk or a piece of satin and characteristic of some minerals in fibrous aggregates (examples are fibrous gypsum [CaSO₄ ∙ 2H₂O], known as satin spar, and chrysotile asbestos [Mg₃Si₂O₅(OH)₄]); and adamantine, having the
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…milky quartz may exhibit this); silky, descriptive of the lustre of a skein of silk or a piece of satin and characteristic of some minerals in fibrous aggregates (examples are fibrous gypsum [CaSO₄ ∙ 2H₂O], known as satin spar, and chrysotile asbestos [Mg₃Si₂O₅(OH)₄]); and adamantine, having the
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