WHERE TRUST IS A TRADITION

Precious Stone

Sapphire34

Sapphire (Greek: sappheiros) refers to gem varieties of the mineral corundum, an aluminium oxide of a colour other than red (in which case the gem would instead be a ruby). Trace amounts of other elements such as iron, titanium, or chromium can give corundum a blue, yellow, pink, purple, orange, or greenish tint. Pink-orange corundum are also sapphires, but are instead called padparadscha.

A sapphire is a gemstone commonly worn as jewellery. Sapphire can be found naturally, or manufactured in large crystal boules. Because of its remarkable hardness, sapphire is used in many applications, including infrared optical components, watch crystals, high-durability windows, and wafers for the deposition of semiconductors.

Sapphire is the birthstone associated with September and the 45th wedding anniversary is known as the sapphire anniversary.

Natural sapphires

Although blue is the most well known hue, sapphire may also be colourless, and also occurs in the non-spectral shades of grey and black.

The cost of natural sapphire varies depending on their colour, clarity, size, cut, overall quality as well as geographic origin. Significant sapphire deposits have been found in Eastern Australia, Thailand, Sri Lanka, Madagascar, East Africa and in the United States at various locations like Gem Mountain the Missouri River, Montana. Sapphires and rubies are often found together in the same area, but one gem is usually more abundant.

Blue sapphire

Colour in gemstones breaks down into three components: hue, saturation, and tone. Hue is most commonly understood as the "colour" of the gemstone. Saturation refers to the vividness or brightness or "colourfulness" of the hue, and tone is the lightness to darkness of the hue. Blue sapphire exists in various mixtures of its primary and secondary hues, various tonal levels (shades) and at various levels of saturation (brightness): the primary hue must, of course, be blue.

Blue sapphires are evaluated based upon the purity of their primary hue. Purple, violet and green are the normal secondary hues found in blue sapphires. Violet and purple can contribute to the overall beauty of the colour, while green is considered to be a distinct negative. Blue sapphires with no more than 15% violet or purple are generally said to be of fine quality, whilst blue sapphires with any amount of green as a secondary hue are of considerably lower quality. Grey is the normal saturation modifier or mask found in blue sapphires, it reduces the saturation or brightness of the hue and therefore has a distinctly negative effect.

The colour of fine blue sapphires can be described as a vivid medium dark violet to purplish blue where the primary blue hue is at least 85% and the secondary hue no more than 15% without the least admixture of a green secondary hue or a grey mask.

The 422.99 carats (84.60 g) Logan Sapphire in the National Museum of Natural History, Washington D.C. is one of the largest faceted gem-quality blue sapphires in the world.

Fancy colour sapphire

Yellow and green sapphires are also commonly found. Pink sapphires deepen in color as the quantity of chromium increases; the deeper the pink color the higher the monetary value as long as the color is trending towards the red of rubies.

Sapphires also occur in shades of orange and brown and colorless sapphires are sometimes used as diamond substitutes in jewelry. Padparadscha sapphires often draw higher prices than many of even the finest blue sapphires. Recently, more sapphires of this color have appeared on the market as a result of a new artificial treatment method that is called "lattice diffusion"

Colour change of a sapphire

A rare variety of sapphire, known as the colour change sapphire, exhibits different colours undr different light. Colour change sapphires are blue in outdoor light and purple under incandescent indoor light. Colour changes may also be pink in daylight to greenish under fluorescent light. Some stones shift colour well while others only partially, in that some stones go from blue to bluish purple. While colour change sapphires come from a variety of locations, the gem gravels of Tanzania are the main source.

Mining

Sapphires are mined from alluvial deposits or from primary underground workings. The finest specimens were mined in Kashmir, in the northwestern section of India, from about 1880 to 1920. These Kashmiri sapphires are considered to be the finest in blue sapphires as the stones have a velvety look. Myanmar, Madagascar, and Sri Lanka are all popular sites, the latter being from where the Logan Sapphire and the Star of Bombay originate.

Sapphires are also mined in Australia, Thailand, and China. Madagascar leads the world in sapphire production (as of 2007) specifically in and around the city of Ilakaka. Prior to Ilakaka, Australia was the largest producer of sapphires (as of 1987). Sapphires are found everywhere including on the ground and in the river mud. India, Pakistan, Afghanistan, Tanzania, and Kenya also produce sapphires, and less commercially significant deposits are found in many other countries.

The US state of Montana has produced sapphires from both the El Dorado Bar and Spokane Bar deposit near Helena. Well-known for their intense, pure blue colour, Yogo sapphires are found in Yogo Gulch, near Utica, Montana. Gem grade sapphires and rubies are also found in and around Franklin, North Carolina, USA. Several mines are open to the public.