How Are Sapphires Formed

Sapphires are the most common colored gemstone, preceded in popularity only by the diamond. Their rich blue hue and rarity have made them a treasured gemstone. They form under very specific conditions in the earth. While blue is the most common hue for sapphires, they are also available in a rainbow of other colors like yellow, pink, orange and white. For thousands of years, humans have worked hard to find gemstone deposits within the earth and have prized gemstones like the sapphire for their beauty and color. The precious sapphire is prized for it's color, durability and rarity. This is what makes it such a popular choice for all types of jewelry like earrings, necklaces and rings.

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Sapphire Origin & Formation

Sapphires are a rare gemstone that can take millions of years to form. Like rubies, sapphires are also formed out of the mineral corundum. In scientific terms the mineral is known as aluminum oxide. Corundum acquires color when there are other minerals that become present as it is forming. Sapphires are typically found in recrystallized limestone and metamorphic rocks that have less silica and a lot of aluminum. When the crystal lattice of the sapphire is forming, if transition metal minerals seep in, the color can transform from white and transparent to a different hue. For this reason, sapphires are also available in various saturations of colors and can even be available in combinations and shades of colors like orange and pink. When corundum takes on a hue other than red, the gemstone is typically classified as sapphire. Different mineral combinations can result in different colors of sapphire. Thus, there are many color varieties in sapphire including pink, yellow and most popularly blue. With iron present, the sapphire can take on a yellow color. With vanadium, purple sapphires are created. And most popular, the blue sapphire is created as a result of titanium being present within the corundum rock. Corundum is found in igneous rocks. When those are cooling slowly, large crystals of minerals can form from those that are present within the magma. The purest sapphires are formed during the transformation of igneous rocks. The more slowly the magma cools, the larger the sapphires will be. Conditions in which magma cools slowly and is untouched by other elements and minerals is rare. In most instances, as the magma is cooling there are almost always changes in pressure and environmental factors. As a result of these changes in environment, each sapphire develops a unique look and color. This is also the reason that inclusions and impurities in the sapphires form. This gives each sapphire a unique look, almost like a fingerprint. No two natural sapphires will ever look exactly the same. Since precise conditions need to exist for a long periods of time as the sapphire is forming, large gemstones are rare. It is quite uncommon to find large natural sapphires, especially those that are free of inclusions. Typically sapphire deposits in the earth are found in a barrel shape that is longer and tapered at the ends and larger in the center. This is simply the way the rough sapphire forms. Once mined, the sapphire can be fashioned into any number of shapes with facets or without. These shapes are then used to craft sparkling jewelry.

Sapphire is a remarkably hard mineral at 9 on the Mohs scale, preceded only by moissanite and diamond. This dense gemstone is a durable choice to craft jewelry that will last for many decades. Sapphire's hardness is the result of strong and short oxygen and aluminum bonds. It's vibrant colors, sparkle and hardness make it so that this gemstone has been prized by cultures and civilizations around the world.

Sapphire deposits can be found in Myanmar, Sri Lanka, Madagascar, Thailand,China, Austrailia, Nepal, Nigeria, Pakistan and Kashmir as well as Montana. Over 150 million years ago, rocks inside the earth's surface were subjected to intense pressure and heat to create deposits of sapphire. In most cases sapphires can be found at 6 to 18 miles underneath the surface of the earth. Over time, weathering and natural movements of the earth's surfaces exposed these sapphire deposits to humans. There are only a few places around the world that have been exposed by weathering to reveal the sapphire deposits within the earth. Sapphires from different locations can have different chemical properties as well as differing microscopic inclusions due to different impurities. Sapphires from around the world can be divided into three main categories that are determined by their formation. These categories are classic metamorphic, non-classic metamorphic, and classic magmatic. Sapphires from Kashmir, Burma and Sri Lanka have historically been the most prized. Burmese sapphires are typically found embedded within marble and are prized for their clarity and quality. Geographically, sapphire deposits can be found along the borderline where the Indian subcontintent pushed into the Asian landmass. When this happened, the intense heat and pressure created deposits of sapphires and over time the water streams and rivers washed away to reveal the deposits. Over time, the wearing away of the earth, made these deposits more readily accessible to humans. For many years, regions in the Asian subcontinent and Asia were famous for their sapphire quality. Recently, Madagascar has become the largest producer of sapphires, and before that Austrailia was the largest producer through the 1990's. Within the United States, Montana and North Carolina are known to produce sapphires. These are known as Montana and Yogo sapphires and have a slightly lighter blue tint. Sapphires are prized from worldover. It is a matter of personal taste, which variety and shade of sapphire is chosen.

The crystallization of a sapphire is divided into two phases, a nucleus forms and subsequent layers of mineral are added over time. If at any time the conditions of the surrounding environment change so that the formation of the sapphire is not longer possible, the nucleus can break apart. Structurally, the sapphire is formed in a hexagonal bipyramid. When mined, sapphires are typically found in a barrel shape due to the way that they form. Almost all sapphires have inclusions. During the formation of a sapphire rutile inclusions can form. These rutile inclusions look like small crystalline growths inside of the sapphire. Natural sapphires can be distinguished from synthetic sapphires by their inclusions. The majority of natural sapphires are heat treated to improve their color. This treatment is permanent. Natural sapphires that are free of inclusions are immensely rare and carry a premium price tag. Four Mine is sure to use only natural sapphires that have been vetted for quality, sparkle and color. We ensure that all our sapphires are sourced from trusted suppliers that use ethical and trusted practices to mine their sapphires. View our classic collection of sapphire jewelry.