Most people think of sapphires only as blue, and probably also associate them with September birthstone rings. They actually come in all kinds of colors and are fascinating stones not only for their geologic properties, but also for their spiritual ones. Sapphire is another name for an aluminum oxide mineral called “corundum” that comes in lots of different colors depending on the presence of elements like iron, titanium, chromium, copper, and magnesium. It can be found naturally in igneous, metamorphic, and sedimentary rocks mostly in South and Southeast Asia (Sri Lanka, Myanmar, Thailand, Cambodia), but also in Africa (Madagascar, Tanzania), Australia, and the US (Montana). When it is red, it is known by the familiar name “ruby.” Orange is particularly rare and is called Padparadscha, derived from the Singhalese word likening it to the color of the lotus blossom. It also comes in pink, purple, yellow, green, colorless, and black. Sometimes the non-blue sapphires are grouped together under the term “fancy sapphire.” Sapphire jewelry can be made from all of them and is one of the most popular gemstones for many reasons, but particularly because of its extreme hardness.
Geologic Properties of SapphiresSapphire is the third hardest mineral, right after diamond and moissanite. It is actually the index mineral for number 9 on Mohs hardness scale. Sapphires can also be made artificially by growing the crystals. This is extremely attractive to optical companies and companies like Apple, who bought nearly six hundred million dollars’ worth of it last year. Synthetic sapphires can be made colorless, plus it is hard, so it’s resistant to scratching, and tough, so it will resist fracturing once a flaw has been initiated, making it great for screens. Artificial stones are also used in sapphire jewelry. They can be produced in any color by adding the exact level of trace element necessary. The main benefit of a synthetic stone, which has the same crystal structure and everything as a natural stone, is that it is more affordable. Some jewelry companies will substitute iolite, blue tourmaline, or blue zircon for sapphire, but these stones are considerably softer than real sapphires and have different healing and spiritual properties, so make sure you know what you are getting.
If a stone is referred to as a “star sapphire,” this means that it contains minor inclusions of the mineral rutile in the underlying crystal structure. When these tiny needles intersect in just the right way, they can form an asterism and look like a six-pointed (or, rarely, twelve-pointed) star on the polished gemstone. There are some extremely famous star sapphires that can be seen in museums, such as the “Star of India” at the American Museum of Natural History right here in New York City and the Star of Bombay at the National Museum of Natural History in Washington, DC.