Difference between Quartz and Quartzite...?
It depends upon how much materials are present, the temperature of the molten material and how fast the material cools.
Combination of space and rate of formation variations affect the size, crystallinity, and purity of pretty well all minerals.
Because of the different environments in which they grew. For a large perfectly formed quartz crystal to form, sufficient space needs to be available for crystal growth and adequate dissolved silica must be available in the magma or hydrothermal fluids.
