1. Transparency test: If you draw a line on a piece of paper and place the "diamond" on the paper, if the line is visible through the "diamond", it is not a diamond, because the diamond will reflect 100% of the light and should not be able to see anything clearly.

2. Humidity test: breathe to the ore, and breathe diffuses very quickly. The surface of a diamond is so smooth that it can't hold water or condensate.

3. Defect test: carefully observe the ore with a magnifying glass. If you can see some small flaws inside the ore, then it is a real diamond. Unless it's a perfectly perfect diamond (which is not possible usually ). Fake diamonds are always very pure and clear.

4. Ultraviolet test: If you have a high-end device, you can view it through ultraviolet light. If it can change color, it is a real diamond, because a real diamond is responsive to ultraviolet light.

With a polariscope

Homogeneous gems can be distinguished from diamonds, spinels, garnets, etc., because zircons are heterogeneous gems, showing an extinction phenomenon of four bright and four dark under a polarizing mirror, while homogeneous gems are completely or porphyritic.

Zircon can be easily distinguished from other similar gemstones by measuring refractive index, density, spectrum, and observing facet edge double and inclusions.

Scientific discovery

The tiny crystals of zircon extracted from rocks on a sheep farm in Western Australia have been examined by scientists and are 4.4 billion years old, making them one of the oldest parts of the Earth's crust.

By examining the rock, geologists determined that Earth's crust formed at least 4.4 billion years ago, just 160 million years after the formation of the solar system.

In addition, scientists believe that the rock's presence shows that the early Earth was not the harsh environment that many scientists have believed. It proves that the Earth once cooled to a temperature that was habitable for life.

Optimization of processing

Heat treatment

Heat treatment can change the color of zircons as well as the type of zircons .

1. Change colors

Zircon from different sources will show different colors after heat treatment.

1) Blue or colorless zircons can be produced by heat treatment under reduced conditions. The most important of these is the Vietnamese reddish-brown raw material of zircon, which after heat treatment produces colorless, blue and golden yellow, the most common variety in gemstone jewelry. Heat treatment steps are as follows:

First of all, the sample is placed in a closed crucible (usually 1kg) and put into the furnace. Under the condition of reduced pressure and reduction, the sample is heated at 900~1000°C, which can make about 30% of the sample reach gem level. The remaining 70% blue zircon with poor color but good clarity can be further heated to produce colorless zircon. The purpose of this heat step is to remove the brown hue from the zircon to produce a colorless zircon with a white fog effect.

2) Heat treatment under oxidation conditions to 900°C produces golden and colorless zircons, some of which may be red in color. Samples that do not achieve gemstone color after the above two steps of heat treatment can also be heat treated into colorless or golden zircon under these oxidizing conditions.

Colorless, blue, yellow and orange-red zircons were obtained by heat treatment. Zircon was still identified as a natural gem because no other material was added during the optimization process of heat treatment. Another process, in which zircons are heated in a crucible for six to eight hours with nitric acid, cobalt, potassium and ferric salts, is relatively rare. The resulting zircons can change color again at extreme temperatures and pressures. For example, blue zircons can turn golden yellow or bright red under extreme high temperature and pressure. Sometimes, such partially colored zircons are placed in a crucible with charcoal and reheated to 800~900°C before turning completely blue again. This phenomenon is closely related to the difference of impurity composition in zircons caused by different origin.

2. Change genres

Heat treatment to 1450°C for a long period of time can cause recrystallization of silicon and zircon, turning the low-type zircon into the high-type zircon. By this treatment, low, medium and high type zircons can increase their densities (up to 4.7g/cm3), have higher refractive index and clear absorption lines, and can also improve their transparency and brightness. Recrystallization caused by heat treatment can also produce fibrous microcrystals, forming cat eyes.

After heat treatment, the surface or edges and corners of zircons become fuller and their glossiness is improved to a certain extent.

Radiation processing

The results of irradiated zircon and heat treatment show an inverse change process. Almost all high-type zircons obtained by heat treatment were irradiated (X-rays, γrays, high-energy electrons, etc.) to restore their pre-heat color, or even to darken. Natural zircons can also become discolored under irradiation. For example, colorless zircons can turn deep red, maroon, purple or orange under X-ray irradiation. Blue zircons can turn brown-reddish brown under X-ray irradiation. However, these irradiated color changed zircons have reversible color changing process and can recover to their original state under extreme high temperature and pressure.