da sapere — December 16, 2018 at 4:00 am

Hot stones




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.

Un sacchetto di rubini estratti in una miniera birmana
Un sacchetto di rubini estratti in una miniera birmana

I rubini sono stati messi in un recipiente al centro del fuoco, dove vengono riscaldati
I rubini sono stati messi in un recipiente al centro del fuoco, dove vengono riscaldati

Warm color
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.




Anello Solis con grande zaffiro giallo non riscaldato, diamanti, platino
Amy Burton, anello Solis con grande zaffiro giallo non riscaldato, diamanti, platino
Anello con rubino sangue di piccione non riscaldato
Anello con rubino sangue di piccione non riscaldato
Anello di platino con diamanti e zaffiro di Oscar Heyman Brothers. Venduto per 215mila
Anello di platino con diamanti e zaffiro di Oscar Heyman Brothers
Rubino grezzo riscaldato
Rubino grezzo riscaldato
Smeraldo colombiano non trattato
Smeraldo colombiano non trattato
Un rubino non trattato: notare le inclusioni e la luce irregolare

Anello con rubino taglio cuscino, del peso di circa 5,25 carati, affiancata su entrambi i lati da un diamante taglio triangolare, montato in platino e oro 18k. Venduto per 1,6 milioni di dollari
Anello con rubino taglio cuscino, del peso di circa 5,25 carati, affiancata su entrambi i lati da un diamante taglio triangolare, montato in platino e oro 18k







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