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Phenacite is found in high-temperature pegmatite veins and is associated with quartz, chrysoberyl and topaz. It has long been known from the Chrysoberyl mine on the Takovaya stream in Russia, where large crystals occur in mica-schist. It is also found with topaz and amazon stone in Colorado and Maine, USA. Large crystals of prismatic habit have been found in a Norway.
The structure consists of a three-dimensional network of corner-linked, slightly distorted BeO4 and fairly regular SiO4 tetrahedra. The lattice of these materials consists of SiO4 and BeO4 tetrahedra, which are bound to each other and form chains oriented along the principal crystallo-graphic axis C3. The chains form voids in the form of wide channels ～4.5? in diameter.