Quartz is a three dimensional network of silica tetrahedra as shown above.
Quartz is mostly crystalline in its arrangement though it may vary in the extent of crystallization. The macro-crystalline variety is the one in which the individual crystal is visible to the unaided eye. The other variety is micro-crystalline or cryptocrystalline, in which aggregates of crystals are visible only under high magnification. The transparent variety tends to be macro-crystalline and the cryptocrystalline varieties are either translucent or mostly opaque.