How Lab-Created Sapphires Are Formed

Lab-Created Sapphires

The composition and physical properties of a created sapphire are exactly the same as a natural stone. A sapphire, at its chemical basis, is aluminum oxide, Al2O3 -- 52.9 percent aluminum and 47.1 percent oxygen. Also referred to as "synthetic" and "simulant," lab-grown jewelry-quality sapphires are made primarily via two methods. The first, the Verneuil flame-fusion process, has its roots in 1902. Each crystal is formed individually, using a blowtorch. Aluminum or titanium oxides, in their purest form, are melted in a small furnace. To produce the desired color, other oxides are added. The crystal, which is called a boule, is formed on a rotating clay peg as it is brought out of the furnace. The second method is called the Czochralski pulled-growth method, which was developed around 1917.

The Czochralski Method

All of the nutrients required to grow a sapphire are melted in a platinum, iridium, graphite or ceramic crucible. A "seed crystal" is then attached to the end of a rod, which is rotated and lowered so that the crystal barely touches the melted mixture. The rod is then brought slowly out of the crucible, at the rate of 1 to 100 millimeters per hour. As the seed crystal is withdrawn, it pulls matter from the melted mixture, which cools and solidifies. Due to surface tension, the crystal remains connected to the molten material and grows until the materials in the crucible have been used up. This growth method can produce very large crystals of extremely high quality; in fact, millions of carats of stones are produced each year using the Czochralski method.

About Sapphires

Sapphires and rubies are the two varieties of the mineral corundum. Sapphires are the second-hardest natural mineral in the world, the first being the diamond. Most blue sapphires are mined in Australia or Thailand, though sapphires can also be gray, black, yellow, pink, purple, orange or a greenish color, and even colorless. Laboratory-created gemstones go through the same process as natural gemstones. The only true difference is that the stone is grown in a lab rather than below the Earth's surface. Man-made sapphires are flawless and much less expensive than natural sapphires, and only a certified gemologist can tell the difference.