Fluorescent test using a regular UV light source will help to distinguish Natural Diamond vs CZ. Cubic Zirconia will not fluoresce unlike Natural Diamonds Fluoresce of about 25% to 30%.
Fluorescence occurs when a gem material is illuminated by radiation of shorter wavelengths with higher energy. A bag of cubic zirconia under LWUV with areas of blue fluorescence that highlights the presence of diamonds. The visible light emitted stops when the source of illumination is turned off.
Ultraviolet Light: About 30% of diamonds will glow blue under ultraviolet lights such as black light. Fake diamonds, on the other hand, will glow other colors or not at all.
Some minerals glow or fluoresce under ultraviolet (UV) light, such as some shown here. Apatite, quartz, orthoclase feldspar, and muscovite under normal white light and UV light.
Do all diamonds fluoresce? No. Only about 25% to 35% of diamonds exhibit some degree of fluorescence in reaction to long-wave UV light.
Cubic Zirconia will not fluoresce unlike Natural Diamonds Fluoresce of about 25% to 30%.
A real diamond appears gray and white inside (brilliance) when held to the light and can reflect rainbow colors (fire) onto other surfaces. A fake diamond will display rainbow colors within the stone when held up to light.
Fluorescence: Sapphires of any color can fluoresce under long wave UV light if iron content is low enough that it doesn't quench fluorescence. Fluorescence colors include pink and red (due to chromium) and orange (due to F-centers or crystal lattice defects according to Vigier & Fritsch, 2023).
Real pearls will display fluoresce under ultraviolet light, meaning they glow. Press a small UV flashlight over a pearl to see if it glows. If the pearl glows, it's likely a real pearl. An authentic pearl displays fluoresce under ultraviolet light because of the presence of natural organic compounds in its nacre.
Cubic Zirconia (CZ) often shows orange fluorescence but in REVERSE ORDER.
Usually fluorescence is blue in color. Less often, a diamond can have yellow or even white fluorescence (other colors too). Diamonds with Strong - or Very Strong - fluorescence can appear quite cloudy, milky or hazy to the naked eye, and emit a prominent and saturated glow in the presence of UV light.
Diamonds glow in black lighting due to a phenomenon called fluorescence and roughly 35% of natural diamonds exhibit some degree of this effect. In nature, the presence of certain chemical impurities within the diamond's composition triggers this glowing effect in the presence of an ultraviolet light source.
In cut stones, cubic zirconia tends to have dull, rounded edges, while diamonds' facets stay sharp. Diamonds rarely show polish marks, but if they do, they will be in different directions on different facets. On the other hand, cubic zirconia will show polishing marks in the same direction on adjoining facets.
If you turn both a diamond and a CZ upside down, the bottom of a diamond will give off the entire rainbow of color reflections, whereas CZs usually have more exclusively orange and blue flashes. This is because cubic zirconias and diamonds have different refractive indexes.
The best way to figure out if a stone is cubic zirconia or diamond is to use your naked eye. Examine the light that emanates from it – a diamond gives off brilliant white light while cubic zirconia will give off a noticeable rainbow of colored light.
Black light test:
When you place a real diamond underneath an ultraviolet light, the stone with fluorescence in it will turn blue. But it's important to know that this will only happen with about one-third of all diamonds. A fake diamond, on the other hand, will almost never look blue under a black or UV light.
Untreated white to cream-colored pearls generally show blue to greenish blue fluorescence under LWUV excitation. Akoya and freshwater cultured pearls, which are rou- tinely processed, typically show strong bluish white fluorescence.
U.V. Fluorescence: weak; blue and colorless topaz may show a weak yellow or greenish glow under long wavelength u.v.. Sherry-brown, pink, or golden yellow topaz may show a strong orange-yellow fluorescence under long wavelength u.v. light that is much weaker under short wavelength u.v. light.
One of the most captivating qualities of hyalite opal is its fluorescent green glow in shortwave ultraviolet light. All minerals can reflect a degree of light, but some have the physical qualities that allow them to temporarily absorb a small amount of light and releases it in a different wavelength.
Place the gemstones in a glass of water and watch. If it floats, then it is probably a fake stone. Real diamonds will sink to the bottom of the glass, while cubic zirconia will float to the surface.
If you visit any jewellery shop and find it difficult to differentiate between these stones, you should observe them in the brightest light. You will see that the diamond has white or silvery sparkles only. However, cubic zirconia will give out colourful sparkles such as red, yellow or blue.
Cubic zirconia also has a higher dispersion rate (between 0.058–0.066 compared with 0.044 of diamonds). The increased dispersion causes the CZ stone to have a “rainbow effect”—meaning it reflects too much colored light. The excess dispersion of light makes it easy to spot as a fake diamond.