Mineral Guide · Mineral

Gyrolite

Gyrolite is a hydrated calcium silicate that forms rounded, radiating aggregates in basalt cavities and other low-temperature environments.

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Crystal structure

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Mineral properties

Formula: NaCa₁₆Si₂₃AlO₆₀(OH)₈·14H₂O
Class: Silicates
Crystal system: Triclinic
Typical colours: colourless, blue-green, white, pale green
Lustre: Pearly, Vitreous
Hardness: 3.50-4.00
Specific gravity: 2.40-2.50
Crystal habit: Botryoidal, Radiating, Spherical
Origin: basalt cavities, zeolite-bearing volcanic rocks and hydrothermal alteration zones

What is Gyrolite?

Gyrolite is a hydrated calcium silicate that forms rounded, radiating aggregates in basalt cavities and other low-temperature environments.

Mineralogy and structure

Reference formula: NaCa₁₆Si₂₃AlO₆₀(OH)₈·₁₄H₂O. Gyrolite has a layered hydrated structure and variable composition. Its spherical aggregates are more characteristic than isolated euhedral crystals. Gyrolite belongs to the silicates and has a triclinic crystal system. Typical hardness is 3.5–4 on the Mohs scale and specific gravity is approximately 2.4–2.5.

Colour and appearance

Typical colours include white, colourless, pale green, blue-green. The usual spherical, radiating, botryoidal habit and pearly, vitreous lustre are useful descriptive features, but colour alone is not diagnostic.

Formation and localities

Gyrolite forms in or is associated with basalt cavities, zeolite-bearing volcanic rocks and hydrothermal alteration zones. Important documented localities include India, Scotland, Northern Ireland, South Africa, Canada and the United States.

Collecting and care

Fragile and hydrated; protect from abrasion, heat and sudden humidity changes.

Sources and editorial review

Reviewed by NotOnlyRocks Editorial Team

Last reviewed: 31 August 2026

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