Re: How to tell the difference between real Diamonds and CZ's.

You asked:

How can I tell the difference between a real diamond, a cubic zerconium, and cut glass without going to the jeweler?

There's a good web page summarizing information about diamonds and simulants which was put together by Dr. Jill Banfield for a course titled Gems and Precious Stones at the University of Wisconsin. It's located at:

http://www.geology.wisc.edu/~jill/Lect6.html

The main difference between glass and diamonds or cubic zirconia is that glass is much softer than either of these materials. Take the stone and try to cut some scrap of glass with it (like an old bottle). If it easily gouges the glass, it's either a diamond or a cubic zirconia. If it doesn't, it's glass.

Cubic zirconia is also softer than diamond so a known diamond should scratch it. You may not want to risk damaging the stone, however. Cubic zirconia also has a higher specific gravity (5.95) than does diamond (3.52) which isn't too difficult to measure if you have the equipment. Read about how to measure the specific gravity of gems at:

http://www.ganoksin.com/borisat/nenam/gravity.htm

Another simple way to distinguish glass from cubic zirconia from diamond is to get a hold of a long-wave ultraviolet light (also called a black light). Diamonds will usually glow blue, cubic zirconia will glow mustard yellow, and glass will not glow at all. Read about the luminescence of various gemstones at:

http://www.geogem.com/luminescence.html