Phenakite's formula is Be 2 SiO 4 . Willemite's formula is Zn 2 SiO 4 . Phenakite is the most well crystallized of the three in general, forming the best crystal shapes and the only one consistently cut as gemstones. Willemite is famous for fluorescing a bright green color under UV light and is found in mass at Franklin and Sterling Hill , New Jersey. Eucryptite is rarely cut as a gem and only some specimens fluoresce a pink color, but none the less it can be a interesting mineral for collectors.
Color is usually colorless or white.
Luster is vitreous. Transparency crystals are transparent to translucent. Some crystals can be well formed with trigonal prisms with rhombohedral terminations. Eucryptite can also replace spodumene forming pseudomorphs. Cleavage in poor in three directions.