Pure corundum is rare and is completely colorless. Color variations arise when small amounts of metallic impurities such as chromium, iron, and titanium substitute for aluminum in the structure. The popular varieties include:
Ruby: The name ruby originates from the Latin word “Ruber,” meaning red. fused alumina manufacturer Any gem-quality corundum with a deep red color is called a ruby.Rubies get their red color due to the presence of chromium.
Padparadscha Sapphire: This rare orange-pink variety owes its unique color to both iron and chromium impurities.
Sapphire: The name sapphire has its origin from the Latin word “Sapphires,” which means blue. It is also thought to have been used in ancient times to refer to lapis lazuli. The name sapphire is a loose term used for all colors of corundum except red. Sapphires can be blue, pink, green, yellow, violet, purple, orange, brown, white, gray, black, and colorless. Theyget their unique color from Fe2+, Fe3+, and Ti4+inclusions.
Emery: It is a black variety of corundum used as an abrasive and for some electrical purposes. The black color is caused by a mixture of magnetite, hematite, and spinel.
The 3C’s of Corundum:
Color :
The pinkish-red, medium to dark red variants of corundum are called ruby. All the other available color variants(gray, blue, blue-green, green, violet, purple, orange, yellow, yellow-green, brown, golden amber, peachy pink, pink, and black), including colorless and white crystals,are called sapphire. They usually have vitreous to adamantine luster with a white streak.
Cut:
As a result of its hardness and durability, corundum is commonly used in jewelry designs that see high traffic or the likelihood of impacts. Corundum should be cut according to its color. fused alumina The red variant should be cut as if it were ruby, while blue variants should be cut according to the uses of sapphire.
Clarity:
Most cut rubies and sapphires contain inclusions. Eye-visible inclusions are lesser desirable than “eye-clean” stones. In some stones, inclusions can make the stone weaker and lead to breakage. Desirable inclusions and fine rutile needles throughout the crystal cause asterism (a phenomenon where gems exhibit star-like patterns when cut en cabochon) and provide a silky texture.
