Cubic Zirconias are a diamond simulant and are colorless where diamonds tend to have a yellow shading. The weight of a CZ is more but since they are usually small it doesn't discourage their appeal.
Source(s):
http://danforthdiamond.wordpress.com/

Permalink | Report

Cubic Zirconia (CZ) is a synthetically created gemstone. It’s actually a man-made crystalline substance created in a laboratory. First cultivated for its potential usefulness in the laser field, cubic zirconia was later developed in the 1970’s as an artificial gemstone.

The one key tell-tale is that cubic zirconia stones are virtually flawless while diamonds almost always have some sort of flaw. That’s the difference between man-made and natural. In those cases, the distinction can only be made by a jeweller’s loupe.
Permalink | Report

CZs have no actual value. They are hard plastic essentially that can be cut with the same number of facets as a diamond, example a round brilliant diamond has 58 facets as a standard, so the round CZ will too. CZs have a plastic and dull look to them if you compare them directly to a diamond. Diamonds come in a range of colors and clarity grades, so no two are ever the same. Maybe some characteristics are, but no two are exactly the same. CZs are all the same. They also exhibit small bubbles within them under a loop or microscope. They are "flawless" and clear to the eye, but they really have no depth and less brilliance than a diamond. It takes looking at a CZ right next to a diamond to see the difference. Once you have done this, you will begin training your eye and it will get easier to distinguish. Also, CZs are lighter than diamonds by about 30%. Diamonds are measured by a weight and not a size measurement. CZs are always measured by a millimeter measurement. Compare a loose 1 carat round diamond next to a supposed 1 carat CZ and the CZ will be noticeably lighter.

CZs are set in everything from base metals to gold to platinum these days, so don't let that fool you. Even some very old, expensive pieces of jewelry may have CZs in them.
Source(s):
None, I'm in the jewelry industry

Permalink | Report

Cubic
Zirconia, CZ Jewelry & Engagement Rings in 14k Gold

Jewelers Studio offers high quality fine cubic zirconia jewelry, cz rings,
engagement ring and wedding bands in solid 14 karat gold.
Permalink | Report