How Are Sapphires Made?

Crystallized Aluminum Oxide

• Sapphires are a type of hematite, a mineral deposit that can be found in many different type of rocks. Aluminum is a form of iron oxide that's an important source for iron ore and pigment. Occasionally, crystallized chunks of these gemstones, which are classified as corundums, occur naturally in the lithosphere, a layer of the earth's crust under extreme heat and pressure. Scientists know that magma flows play a role in the development of naturally occurring conrundums but have yet to pin down the specifics of their origins.

Color

• Pure crystallized aluminum oxide is translucent and clear, but impurities that seep into the crystallization process are responsible for adding color to the stone, particularly chrome, iron and titanium. Depending on which impurities are present in the gemstone, a sapphire can be colored blue, yellow, pink or orange. In top quality stones, these impurities don't interfere with the clarity or luster of the stone, though in the more common and less pure stones, impurities affect the gem-like qualities for which the stone is prized.

Rubies

• Although sapphires occur in nearly every color of the spectrum, centuries-old gemstone tradition deems red and pink crystallized aluminum oxide are referred to as rubies. Although they're treated differently on the gem market because of their different name and color, the only chemical difference between the two stones is the presence of chromium in rubies that give them their red hue. Otherwise, both minerals are identical. These stones are harder than all stones except diamonds, and thus an easy-to-maintain stone prized in jewelry.

Lab-Created Sapphires

• Industrial processes simulate the geologic conditions that give birth to sapphires. Using either a blowtorch to melt aluminum and oxidize it as a crystal, or grown from a superheated solution of aluminum with a crystallized base, engineers simulate the creation of sapphires in a lab. While these gems are usually of a better quality than naturally occurring ones because of quality control standards in the labs, they're still less valuable than natural ones because of the latter's rarity.

Geography

• In addition to whether a sapphire was created in a lab or found naturally in the wild, the spot a naturally occurring sapphire was mined, usually discovered in the sand and silt in streambeds, plays a factor in determining its worth. Naturally occurring stones discovered in Burma, Sri Lanka and Kashmir usually fetch the best prices on the gemstone market, provided they haven't been heat-treated. Other sources, such as India and North America, are also known for producing mid- to high-quality stones.