Sapphires: The September Gemstone

Sapphires like rubies are a variety of the gemstone corundum. It is a very hard stone, ranking a nine on the Mohs scale. The chemical make-up of the stone is Al2O3 - 52.9 percent aluminum and 47.1 percent oxygen1. There are traces of iron and titanium in the blue stone.

Although most people think of sapphires as being blue, they can come in a variety of colors. Even so, in the gem trade, it is primarily the blue stones which are called "sapphires". Other colors normally have their color name precede the word. Sapphires with a color other than blue are often called "fancy"2. The crystal is mined in many regions of the world and those from each mine have their own unique chemical signature that can be determined by gem experts. Probably the most prized sapphires come from Kashmir. They are also called "Cornflower Sapphires" because of the coloration. Prized sapphires might also come from Sri Lanka and Madagascar. They have also been mined in North Carolina and Montana, in the United States.

Sapphires may contain asterisms, which make the light reflect in star-like patterns that seem to move when the stone is moved. Asterisms are caused by small metal fiber "inclusions" within the stone. Heat treatment of colorless corundum can actually turn it a bluer color. However, this treatment tends to detract from the ability of gemologists to trace the origin of the stones, giving them less value than more natural gems.

Those born in the Month of September can boast the sapphire as their birthstone. The word "sapphire" derives from the Latin word, sapphirus which, not surprisingly, means "blue". Yet the Latins borrowed the Greek word: sappheiros which meant "blue stone". Ironically the Greek word probably referred to a different gemstone, the lapis lazuli. Yet other etymologists believe "sapphire" may have come from the Hebrew sappir.3

Sapphire Watch Glass

The sapphire is a very popular gem in jewelry and can be found in rings, pendants, necklaces, bracelets and more. Some of these stones have been carved into small cameos. Synthetic sapphire has found many industrial and commercial uses. Sapphire and ruby balls make excellent bearings. They have a heat resistance level up to 2000° C and have minimal wear and tear compared with other materials4. For this reason many scanner windows have a sapphire laminate coating to prevent scratching that obscures the ability of scanners to read codes. Quality watch glasses also often have the same coating. They can also be used in lasers, and precision electronic instrumentation.

Synthetic sapphires are made using a Verneuil process, or some variation on Flame Infusion. Aluminum oxide is melted down and a seed crystal is introduced and spun or drawn forth while the mixture cools. (For more details on this process see Synthetic Rubies.)

< Emeralds | Ruby >

  1. Sapphire Origins
  3. Origin of the Word, Sapphire might also have been Sanskrit.
  4. Ball Bearings

Interesting Fact:

The first synthetic sapphire was made in 1902. A synthetically grown sapphire is hard to distinquish from a natural sapphire, but is characterized by fewer inclusions.

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