Phyllosilicate (sheet silicate) gyrolite group
Specific Gravity: 2.36 to 2.45
Hardness: 3 to 4
Colour: Brown, colourless, white, green
Solubility: Decomposed by acids
Common impurities: Fe, Mg
Gyrolite is a secondary mineral that occurs in amygdules in hydrothermally
altered basalt and basalt
tuff (Dana, Mindat). It has also been found in a pegmatite dike intruding
It is stable under saturated steam conditions from 120 to 200oC
Associated minerals include apophyllite, stilbite, laumontite, thomsonite, okenite, tobermorite, xonotlite and calcite (HOM).
The type locality is The Storr, Portree, Trotternish, Isle of Skye, Highland, Scotland, UK.
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