Precious and semi-precious stones in the great majority are heated at high temperatures. That’s why ♦
If the precious stones warm your heart is perhaps because in turn have been heated. Not from your eyes, but from an electric furnace which can reach 1,600 degrees. The thermal treatment of precious and semiprecious stones is known to jewelers and gemologists, but little known to the general public, that is, those who buy jewelry that flaunt jewels of deep red, deep blue sapphires, aquamarines transparent. In fact the colored stones that are sold as natural are a small minority, most end up in the oven, without the intervention of a chef. We see, then, what is the heat treatment of gemstones.
The stones are heated above all to bring out the colors. During treatment the stone is heated to very high temperatures (up to about 1600 degrees Celsius). at this temperature the inclusions (small amounts of other minerals) present in the stone melt and add their own color to the stone. Usually, therefore, the heated stone becomes darker, of a more intense hue. This is the case, for example, of rutile in the blue sapphires. There are also sapphires, known as Gouda, which are extracted from the ground milk and white sapphires turn blue when heated. Even the rubies are almost always heated (except exceptions): with the heat the aluminum oxide in the stone creates a new crystalline structure and the chromium is combined in a different way, allowing a better shade of red. Another effect of the heat is that it can improve the transparency of the stone, thanks to the destruction of any gas or fluid inclusions.
How to find them
Do you have a ring with a natural stone or heated? The question should be: what does it matter? But if you are curious to know, you must contact a gemologist with a microscope. And even so will not be easy to find out. The gemologists, however, can examine the internal state of the stone, inclusions, and look for signs of heat treatment. In general, if the stone is perfect or has exceptional value, or has been treated.
What stones are heated
Here the stones more easily end up in the oven: amethyst, citrine, ametrine, aquamarine, tourmaline, topaz, sapphire, ruby, tanzanite, blue zircon.