Snapple just taught me that quartz crystals oscillate at 32,768 Hz, and multiple sources confirm this. Couldn't help but notice that's a power of 2. Coincidence or not?
It may be sufficient. Since quartz is doubly refractive, a sharp eye can often observe the doubling of facet junctions when observed through the table. The junctions may look more fuzzy than doubled. Do some practice comparisons with stone you know are glass and quartz. It will help you train your eye.
I think so. There is an excellent article of the difference between glass and quartz (see sources) at Wehug. First distinction between glass crystal and quartz crystal - both items contain Silicone Dioxide but glass products have much less Silicone Dioxide than natural quartz crystals. Second difference between quartz verses glass, the structure of the material. Quartz items have a very definite crystalline structure and glass has a liquid like non crystalline structure. The molecules in quartz are lined up and the molecules in glass are random. And a second site when discussing jade and glass says: Long used as a jade simulant, glass is almost always discernible by gas bubbles in its interior, (a 10x loupe is sufficient). I hope this helps.