But if the formula of quartz is written as SiSiO 4 then the similarity is obvious. The reason that berlinite is able to have the same structure as quartz is because the aluminum and phosphorus ions are of similar size to silicon ions. Thus the same structure can be achieved since the aluminums and phosphorus can completely replace the silicons without alteration of the quartz structure. Unfortunately, berlinite rarely forms crystals. It would be fascinating to compare the crystals of berlinite to those of quartz.
Color is colorless, gray to pink or rose.
Luster is vitreous. Crystals are transparent to translucent. Cleavage is absent. Fracture is conchoidal. Streak is white or gray.