How can I tell the difference beween coloured glass and a cubic zirconia?

Question

In the old days, glass was usually coated on the back to keep the colour, and stones, had no coating. But now with completely coloured glass how can one tell?

Answer 1

There are several easy methods. The first is the difference in hardness. The Cubic zirconia will be about 8.5 on the Mohs scale. This is harder than glass.

Another way might be to find the density. Few glasses have a specific gravity betwenn 5.6 and 6 (which is the range for CZ).

If you can measure the dispersion of the light through the gem, the Cubic zirconia will be very high (near .60) which is even higher than that for diamond.

The fastest way for most people without specialized knowledge or equipment is to place the "stone" under a shortwave Ultraviolet light. The CZ will luminesce yellow, greenish-yellow or a shade of tan.

Answer 2

Yes, but it can also go undetected, even by those who have equipment designed to spot authenticity. There are various qualities of cubic zirconia as well as diamonds. So, lower quality cubic zirconia is very easy to detect. If it is a large stone it is very easy to tell with the naked eye. But if the stones are really tiny it is difficult to tell. I purchased a cubic zirconia ring from Sears for $500 in1999 with a lot of very small stones cumulating 5 ct. Subsequently, at a pawn shop in 2002, I was interested in how they determine the difference between the two.They had a large selection of jewelry on display labeled cz or diamond. I had my ring tested without saying what it was. They used the eyepiece thing and a "diamond tester", and informed me the ring had diamonds and 14kt gold! It did have 14kt gold, but not 5 carats of diamonds. I asked what the "diamond tester" did, and they said it measured the density of the stones, with diamonds being more dense than cz. The device beeps upon measuring the density of a diamond. So- I think it's hard to say yes or no, depending on the actual skill & knowledge of the analyzer. If presented to an educated & experimented analyzer the difference is detectable.

Answer 3

Without any special equipment, examine the facet edges. In glass they can appear rounded or the surface of the stone may be pitted. In glass, air bubbles are not uncommon, whereas you will never see them in CZ. The facet edges of CZ look real sharp. Also, it is so much harder than glass that it would be able to put a scratch on a window, for instance. CZ also splits the light into rainbows, (dispersion) way better than glass, so it's brighter...more attractive.