Formula: LiAlSiO4 Inosilicate (chain silicate), phenakite group
Specific gravity: 2.657 to 2.666
Colour: Colourless, white, pale tan, pale grey
Solubility: gelatinises in acids
Common impurities: Na,K
Eucryptite occurs in lithium-rich
pegmatites, often as graphic intergrowths with
albite derived from alteration of
Eucryptite is a secondary mineral derived from spodumene and associated with albite, spodumene, petalite, amblygonite, lepidolite and quartz.
The co-occurrence of the lithium aluminium silicates spodumene, petalite and eucryptite is not common, but it does occur in some pegmatites in northern Portugal. The spodumene precipitates early from the magma, petalite later, and eucryptite is hydrothermal and secondary. On alteration spodumene is mainly replaced by albite and muscovite, and petalite by K-feldspar and eucryptite (CM 39.729-746).
spodumene and Na+ to eucryptite, albite and Li+
2LiAlSi2O6 + Na+ → LiAlSiO4 + NaAlSi3O8 + Li+ (AM 67: 97-113
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