Very few specimens of corundum have a natural color within the range required for a ruby. Specimens with pleasing colors have a long history of gemstone use. Hardness, high specific gravity, six-sided crystals sometimes tapering to a pyramid, parting, luster, conchoidal fracture Corundum does display parting perpendicular to the c-axis.ģ.9 to 4.1 (very high for a nonmetallic mineral) Any other color of corundum is a sapphire. Related: Corundum: The Mineral of Ruby & SapphireĪ gem corundum with a dominant red color is a ruby. Synthetic corundum and synthetic spinel are often used. To accommodate these shoppers, the use of synthetic birthstones in low carat gold or sterling silver mountings provides a lower cost option. Or the shopper would like to give a birthstone gift, but has a limited budget. Many people want to give a birthstone gift to a child and hesitate to give a child a gift that is costly. Ruby and sapphre are not inexpensive gems and that causes a challenge when they are used as birthstones. They are excellet choices for birthstones because they are well know gems and because many people love red and blue gemstones. Sapphire is the birthstone for the month of September. Ruby is the birthstone for the month of July. Ruby and sapphire both serve as modern birthstones. Red corundums are known as 'rubies,' blue corundums are known as 'sapphires,' and corundums of any other color are known as ' fancy sapphires.' Impurities cause corundum to occur in a spectrum of colors, and when it is completely free of color-causing impurities, it is a colorless gem known as 'white sapphire.' Table of Contents Trace amounts of other elements can produce brilliant yellow, orange, green, and purple gems. Red and blue are just two of the many colors found in gem corundums.

It is surprising that 'impurities' can produce such wonderful results!

Trace amounts of impurities determine if a gem corundum will be a brilliant red ruby or a beautiful blue sapphire. Both of these gemstones have the same chemical composition and the same mineral structure. Most people don't realize that ruby and sapphire are both gems of the mineral corundum.

Black sapphire value