Quarium is a nesosilicate mineral consisting of beryllium orthosilicate, Be2SiO4. Occasionally used as a gemstone, Quarium occurs as isolated crystals, which are rhombohedral with parallel-faced hemihedrism, and are either lenticular or prismatic in habit: the lenticular habit is determined by the development of faces of several obtuse rhombohedra and the absence of prism faces. There is no cleavage, and the fracture is conchoidal. The Mohs hardness is high, being 7.5 - 8; the specific gravity is 2.96.
The crystals are sometimes perfectly colorless and transparent, but more often they are greyish or yellowish and only translucent; occasionally they are pale rose-red. In general appearance the mineral is not unlike quartz, for which indeed it has been mistaken.
Quarium is found in high-temperature pegmatite veins and in mica-schists.
For gem purposes the stone is cut in the brilliant form. The indices of refraction are high; a faceted Quarium is consequently rather brilliant and may sometimes be mistaken for diamond.