Sapphire

SAPPHIRE

Corundum is the mineral species that includes all sapphires and rubies.

Rubies are red corundum; sapphires are corundum of the remaining colors of the rainbow including clear. Sapphire is usually used for the color blue and all other sapphires are considered fancy sapphires.

Blue sapphires are the most popular of all the sapphires. Since it has a relatively high hardness ( 9 on the Mohs scale) it  can be worn daily. Blue sapphire works well in either yellow gold, white gold, or platinum. The best sapphires display a pure blue hue with no modifying colors.  If there is a secondary color,  violet is the next in value. A green secondary color will bring down the value.

Sapphire is a gem that has been mined for over 2000 years. In ancient myth, blue sapphire’s color came from exposure to the sun.  The longer the exposure, the richer the color blue. The blue actually comes from trace elements in corundum. All corundum is created from  the elements oxygen and aluminum. The three most common elements on the earth are oxygen, aluminum, and silicon. Corundum forms in an environment that is free of silicon. In its pure state, corundum is clear. The trace elements of titanium and iron give corundum its blue color. The more iron in a gemstone, the darker blue the sapphire.

Blue sapphires originate in both basaltic and non-basaltic environments.  Sapphires found in basaltic rock have medium and good color, and a richer iron content will make them darker. The sapphires found in association with marble and limestones have less iron and are not as dark. Blue sapphire crystals are found in sizes ranging from a few points into hundreds of carats.  Most commercial grade sapphires are less than 5 carats. There are larger blue sapphires found than there are large rubies found. The rough crystals will influence the finished gem size and shape. The crystals are barrel shape, spindle shape, hexagonal pyramid shape, or bipyramid.  The color in sapphires can be distributed in zones and the cutter needs to cut the sapphire to concentrate the color in the gem in a way that the location of the color zone will offer the best return of the color when looking at the gem from the top. Sapphires are also pleochroic, which means the gem can display different hues depending on how the gem was cut out of the crystal.  If the table (top of gem) is cut perpendicular to the long length of the crystal, the sapphire will be bluer.  If the table is cut parallel to the long length of the crystal, then the sapphire will be greener. To achieve a rich lively blue, darker sapphires are cut shallower to lighten the color and lighter crystals are cut with a deeper pavilion to create a darker blue.

Sapphire is a gem that has been mined for over 2000 years. In ancient myth, blue sapphire’s color came from exposure to the sun.  The longer the exposure, the richer the color blue. The blue actually comes from trace elements in corundum. All corundum is created from  the elements oxygen and aluminum. The three most common elements on the earth are oxygen, aluminum, and silicon. Corundum forms in an environment that is free of silicon. In its pure state, corundum is clear. The trace elements of titanium and iron give corundum its blue color. The more iron in a gemstone, the darker blue the sapphire.

Blue sapphires originate in both basaltic and non-basaltic environments.  Sapphires found in basaltic rock have medium and good color, and a richer iron content will make them darker. The sapphires found in association with marble and limestones have less iron and are not as dark. Blue sapphire crystals are found in sizes ranging from a few points into hundreds of carats.  Most commercial grade sapphires are less than 5 carats. There are larger blue sapphires found than there are large rubies found. The rough crystals will influence the finished gem size and shape. The crystals are barrel shape, spindle shape, hexagonal pyramid shape, or bipyramid.  The color in sapphires can be distributed in zones and the cutter needs to cut the sapphire to concentrate the color in the gem in a way that the location of the color zone will offer the best return of the color when looking at the gem from the top. Sapphires are also pleochroic, which means the gem can display different hues depending on how the gem was cut out of the crystal.  If the table (top of gem) is cut perpendicular to the long length of the crystal, the sapphire will be bluer.  If the table is cut parallel to the long length of the crystal, then the sapphire will be greener. To achieve a rich lively blue, darker sapphires are cut shallower to lighten the color and lighter crystals are cut with a deeper pavilion to create a darker blue.

Blue sapphires originate in both basaltic and non-basaltic environments.  Sapphires found in basaltic rock have medium and good color, and a richer iron content will make them darker. The sapphires found in association with marble and limestones have less iron and are not as dark. Blue sapphire crystals are found in sizes ranging from a few points into hundreds of carats.  Most commercial grade sapphires are less than 5 carats. There are larger blue sapphires found than there are large rubies found. The rough crystals will influence the finished gem size and shape. The crystals are barrel shape, spindle shape, hexagonal pyramid shape, or bipyramid.  The color in sapphires can be distributed in zones and the cutter needs to cut the sapphire to concentrate the color in the gem in a way that the location of the color zone will offer the best return of the color when looking at the gem from the top. Sapphires are also pleochroic, which means the gem can display different hues depending on how the gem was cut out of the crystal.  If the table (top of gem) is cut perpendicular to the long length of the crystal, the sapphire will be bluer.  If the table is cut parallel to the long length of the crystal, then the sapphire will be greener. To achieve a rich lively blue, darker sapphires are cut shallower to lighten the color and lighter crystals are cut with a deeper pavilion to create a darker blue.

Most sapphires have some inclusions, although they do have better clarity than ruby. The sapphires that have high clarity are very valuable, and usually unheated.  Ninety-five percent of all sapphires are heated to improve color and clarity. Rutile needles, silk, boehmite needles, included crystals, fingerprint inclusions, growth and color zoning are the common inclusions in a sapphire. Rutile needles in a sapphire are tiny inclusions that catch the light and make the sapphire have a velvety luminosity, which is highly valued.

 Heat treatment of sapphires can increase the blue coloration, lighten darker gems, fill fractures, and remove silk to improve clarity and transparency. Sapphires have been heat treated for over 2000 years, but it was not until the 1970’s when the technology for heat treating at high temperatures was developed. Some rough crystal that do not even show a blue color can be heated and this  intensifies the trace elements creating a blue crystal. This rough can be milky white to a brownish smoky color.  Heating to 1600˙ F – 2900˙F will turn these gems into a desired blue.

 Another treatment used with sapphires is lattice diffusion. In this process the sapphire is packed in a crucible with coloring agents such as titanium or beryllium and then heat until almost the melting point. The elements become a part of the composition of the sapphire;  titanium forms on the surface and beryllium penetrates into the sapphire.

3.47cts. Ceylon Cushion Cut Sapphire, unheated.

The most valuable of sapphires have no treatment beyond cutting and polishing. Unheated from Kashmir, Myanmar, and Sri Lanka is the most valuable. The ones that are heat-treated are the most common and not as valuable as the untreated sapphire. Lattice diffusion is the least valuable sapphire.

 Many blue sapphires color is described by a mining location in the trade. This label does not mean that the gem is from that location, but the color is similar to the sapphire that is usually found in that location. A sapphire’s origin can be determined through a gem laboratory, without that determination in a report, origin cannot be verified.

2.47cts. Ceylon Emerald Cut Sapphire

A “Kashmir” color is violetish-blue to a pure blue hue, with vivid saturation and medium to dark tone. The color is sometimes called Cornflower blue. There is very little chromium in these sapphires, so they tend to be mostly a true blue. These gems have the tiny inclusions, rutile needles, which create a velvety luster and softness. Sapphires such as these are the finest quality sapphires.

A “Burmese” sapphire color is a slightly violetish blue to blue hue. They have a strong to vivid saturation and medium to dark tone blue. Iit lacks the velvety luster of the Kashmir and the color is a royal blue and  considered of very fine quality.

A “Ceylon” or “Sri Lankan” sapphire color is a violetlish blue to blue hue;  some can be slightly grayish. The saturation is strong with light to medium light tone returning more light to the viewer. These usually have greater brilliance. These also are considered of very fine quality.

A “Thai” sapphire color is violetish blue to slightly greenish blue with a medium to dark tone. These are often described as inky blue or blue black. These are more commercial grade sapphires.

Sapphires are found in many locations throughout the world.  The deposit in Kashmir was exposed through a landslide in the Zaskar range in 1881. The tailings from the landslide were mined from 1881 through 1887. These tailings from the landslide were completely mined out by 1930. There have been very little sapphires out of Kashmir since then. There are most likely more sapphires in Kashmir, but it is difficult to get to them due to elevation, difficult terrain, and political situations.

In Myanmar, formerly Burma, sapphire and ruby have been mined for over 800 years. Blue sapphires form in association with ruby in the marble host rock. Ninety percent  of the gems found in this region are ruby and 10% are blue sapphire. Most are alluvial finds. Mining is sporadic due to the difficulty in accessing the region, as well as the political and economic conditions of Myanmar. Some of the highest valued sapphires come from this region. The color is a rich intense royal blue, maintaining its color in all lighting conditions. Most are heated to create a more crystalline appearance.

Sri Lanka has been a source for blue sapphire for over 2000 years. It is all alluvial mining by small operations. By law mining is done using simple, non-mechanized equipment providing their citizens with a lasting source of employment. Sri Lanka produces larger crystals, remarkable brilliance and highly saturated blue, bright in appearance due to less iron in the crystals.

Thailand has been a source for sapphires. The sapphires in Thailand tend to be the darker inky blue sapphire, The Chantaburi region is the oldest mining area in Thailand. In 1918 sapphire was discovered in Kanchanburi of mostly commercial grade sapphire. The mines in Thailand are not producing much now. Thailand remains important in the sapphire marketplace since the majority of cutting, treating, and marketing of sapphires takes place there. Sri Lanka, Cambodia, Myanmar and Australia sends their rough to Thailand to process.

The sapphires in Cambodia are found in Pailin, near the Thai border. There are some fine quality blue sapphires as well as small sizes in commercial quality sapphires. They are found in an alluvial deposit and are similar to the Thai sapphires since they are formed in the same manner. Most of these sapphire are heat treated. The mining is sporadic due to political situations in Cambodia.

In the 1990’s, sapphires have been found in Africa in a rich deposit from Kenya, Ethiopia, Tanzania, and Mozambique. The Umba valley and the Tunduru are rich in all colors of sapphires including ruby and the African padparadscha.

Australia has abundant commercial grade sapphires. They are iron rich and dark inky blue to some having a greenish tint. The mining in Australia is mechanized and almost all are heat-treated.

In the 1990’s, Madagascar, a source of good to fine blue sapphires were in the league of Sri Lanka and Kashmir sapphires. The commercial grade is good quality sapphires. The crystals are an elongated, tubular shape, barrel shaped, and bipyramid. There are slight inclusions and most are heat- treated. In the northern region the host rock is basaltic and in the southern are metamorphic marble as in Kashmir and Myanmar.

In  Montana, United States, the sapphire mined are small crystals, most under a carat in size. Yogo Gulch is where they are deep mined. Eighteen million carats over the past 100 years. The color is uniform and light blue and good clarity. These sapphires are not heated. In the southern part of Montana are alluvial deposits of sapphires and these have more inclusions and are heated. These mining areas are called Dry Cottonwood Creek and Rock Creek.

Other locations for blue sapphires are China, Vietman, Laos, Nigeria.