Amethyst is a variety of crystal quartz.
Pure quartz is a homomogeneous crystal.
Quartz.
The scientific name for quartz crystal is silicon dioxide (SiO2).
There are several differences, the primary one being that on the Mohs hardness scale, diamond is 10, quartz is 8. Quartz crystal is very hard, but diamond is harder.
quartz crystal
A tabular crystal habit refers to the appearance of a mineral crystal as a somewhat flat, tablet shaped form.
Rainbow quartz is a term used for describeing two states of quartz crystal. One state, is a quartz crystal that has been fractured internally. The refraction of light through the crystal, produces a rainbow color spectrum. The second state, are quartz crystals that have been coated in titanium. The coating gives the surface of the quartz a rainbow effect.
Piezo-electric Effect
Not much. Quartz is almost completely insoluble in water.
mm
A Quartz crystal is worth about 20$-35$ an ounce.