What is Eucryptite?
Eucryptite is a lithium aluminium silicate of the phenakite group, most often found as massive material or as rare crystals embedded in pegmatites.
Mineralogy and structure
Reference formula: LiAlSiO4. Eucryptite is trigonal and may show aluminium-silicon ordering and polysynthetic twinning. Its ideal formula is LiAlSiO4, but natural material can contain minor sodium or potassium.
Colour and appearance
Typical colours include colourless, white, pale tan, pale grey. The usual massive, granular, prismatic habit and sub-vitreous, resinous, greasy lustre are useful descriptive features, but colour alone is not diagnostic.
Formation and localities
Eucryptite forms in or is associated with lithium-rich granitic pegmatites and altered albite-bearing zones. Important documented localities include the United States, Brazil, Zimbabwe, Canada and other lithium pegmatite districts.
Collecting and care
Stable for display; preserve the pegmatite association because massive eucryptite is difficult to identify by appearance alone.
Eucryptite in popular symbolism
Modern crystal guides sometimes associate Eucryptite with symbolic themes based on colour or collecting tradition. These associations are cultural interpretations, not mineralogical or medical properties.
