Eucryptite is a rare silicate mineral and it is one of very few silicate minerals that have a symmetry that is trigonal. It really is a known person in the Phenakite Group of minerals that includes Eucryptite, Phenakite and Willemite. All three have a similar chemical that is basic and symmetry, but different steel ions. Eucryptite can fluoresce a magenta that is gorgeous to orangish-red underneath shortwave (SW) ultraviolet (UV) light (put your mouse within the picture above to start to see the gems color under SW-UV light).

Eucryptite ended up being called in 1880 by United states mineralogists George J. Brush (1831-1912) and Edward S. Dana (1849-1935) from the words that are greek well and concealed, in reference to its occurrence as intimate intergrowths with Albite.

Eucryptite are available in the united states, from Branchville, Fairfield County, Connecticut; Center Strafford, Strafford County, New Hampshire; in the Harding pegmatite, Dixon, Taos County, brand new Mexico; in the Midnight Owl pegmatite, Maricopa County, Arizona; as well as in the Foote mine, Kings Mountain, Cleveland County, new york. From the Tanco pegmatite, Bernic Lake, Manitoba, and near Nakina, Ontario, Canada. In Zimbabwe, large amounts at Bikita, with many other localities that are minor. From the Haapaluoma quarry, near Peräseinäjoki, Finland.

Category: Silicate mineral
Chemical Formula: LiAlSiO4
Lithium Aluminum Silicate
Molecular Weight: 126.01 gm
Composition: Lithium 5.51 % Li 11.86 % Li2O
Aluminum 21.41 % Al 40.46 % Al2O3
Silicon 22.29 % Si 47.68 % SiO2
Oxygen 50.79 % O
  100.00 % 100.00 % = TOTAL OXIDE


Crystallography: Trigonal – Rhombohedral
Crystal Habit: Rare euhedral crystals, to 3 cm; common forms are {1010}, {1120} and {0001}. In coarse crystalline aggregates and massive.
Twinning: None


Cleavage: Poor/indistinct on {1010} and {0001}
Fracture: Irregular/Uneven, Conchoidal
Tenacity: Brittle
Moh’s Hardness: 6.5
Density: 2.657 – 2.666 (g/cm3)
Luminescence: Fluoresces pink to magenta-red or orangish-red under SW UV
Radioactivity: Not Radioactive


Color: Colorless, White, Tan, Gray
Transparency: Transparent to translucent
Luster: Vitreous
Refractive Index: 1.570 – 1.587  Uniaxial ( + )
Birefringence: 0.0130
Dispersion: None
Pleochroism: None