Synthetic Ruby & Sapphire
Verneuil developed flame fusion primarily for the synthesis of ruby, but the same method can be used for the creation of other gem materials, including sapphire, star sapphire, spinel, rutile and strontium titanate. The basic concept of the flame fusion method is to take the raw gem material, melt it, and then allow it to recrystallize. The concept is simple, but this method depended on some key bits of technology. First, it was necessary to have extremely pure material to begin the process with. In the case of ruby or sapphire, this meant aluminum oxide that was free from impurities such as sodium. The earliest attempts to recrystallize ruby were actually accomplished by melting natural ruby crystals, due to the lack of fine, pure aluminum oxide.
During the Verneuil process, the powdered aluminum oxide is released down a tube where it passes through a flame that melts the material into small droplets. These droplets fall onto an earthen support rod placed at the bottom of the furnace. The droplets form a single crystal called a boule. The boule has a characteristic cylindral shape with a tapered end. It is usually about 13 to 25 millimeters in diameter, 50 to 100 millimeters long, and weighs 75 to 250 carats. Crystals produced by the Verneuil flame fusion process are chemically and physically equivalent to naturally occurring crystals, and strong magnification is usually required to distinguish between the two. One of the signature characteristics of a Verneuil crystal is curved growth lines, which form as the cylindrical boule grows upwards in an environment with a high thermal gradient. The equivalent growth lines in natural crystals are parallel.
|
- First Published: April-07-2008
- Last Updated: August-23-2017
- © 2005-2018 GemSelect.com all rights reserved.
Reproduction (text or graphics) without the express written consent of GemSelect.com (SETT Company Ltd.) is strictly prohibited.