Beryllonite is a sodium beryllium phosphate. The mineral is named after its high beryllium content. Beryllonite is a very rare gem. Crystals can range in color from colorless to white, or pale yellow.
Beryllonite rates only a 5.5 on the hardness scale, making it quite a soft stone. Because of its low hardness, brittleness and perfect cleavage, it is an extremely fragile stone, and thus is only faceted for collectors, who know to take great care of it.
Beryllonite is also a very dull gemstone, because of its weak fire and low dispersion. It has been known to be mistaken for other colorless gemstones with low dispersion.