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Sapphire: description, properties and photo

Sapphire

Sapphire is a precious gemstone, variety of corundum mineral. The name is translated from different languages ​​as «blue stone». The beauty and physical properties of the stone have been appreciated for many centuries. The blue color is classic for it. There are also sapphire varieties of other colors: yellow, pink, purple, green, black, etc. This colors are called multi-colored or fancy sapphires. Among all the varieties of corundum, the blue in the classification are the most expensive.

Sapphire properties

Precious sapphire is a corundum mineral, colored with titanium and iron. In addition to the primary color, it may have shades of purple or green. Pure spectral blue color without additional shades is the highest appreciated. In its commercial classification, two main expensive colors are indicated: “Royal Blue” (saturated dark blue) and “Cornflower Blue”. Untreated samples are the most valuable.

Corundum is a mineral with hardness 9 in Mohs scale, just diamond is harder. This property is highly valued In jewelry creation, because such stone is less exposed to wear. Crystals of natural corundum rare come in large size, they are characterized by irregular zonning. The combination of rarity and high quality characteristics is typical for specimens from Kashmir (India), Myanmar (Burma) and Sri Lanka (Ceylon). Characteristics of stones from other deposits can also be good, but they are usually dark in color.

DEPOSITS

The most beautiful classic corundum stones has been mined in the north of India in Kashmir state, but decades have passed and this deposits were exhausted. Nowadays rare untreated faceted Kashmir samples break price records – over $235,000 per carat. At the second place in value are blue and light blue samples from Myanmar (Burma) and then from Ceylon Island. These are the three main “brand” deposits of sapphires, which are characterized by high quality. Mining of excellent blue sapphires began in Madagascar a few years ago. Sapphires from Thailand, Australia, Cambodia, Laos are often too dark and not large. African (Nigerian and Tanzanian) stones are often far from the best color and usually come with additional shades.

Sapphire Crystal

Properties

Mineral:

corundum

Chemical formula:

Al2O3

Crystal Systems:

trigonal

Mohs scale hardness:

9

Optical character:

anisotropic

Cleavage:

very imperfect

Density:

4.00 g / cm3

Luster:

Vitreous

Refractive index:

1,762-1,770

Birefringence:

0.008-0.010

Dispersion:

0,018

Color:

blue, violetish-blue, greenish-blue

Interesting facts

  • Kashmir is a region in the north of India, where the best and the most expansive sapphires were mined earlier.
  • Dark color «Royal» is very popular in Asia. In the north countries Cornflower blue sapphires looks better because of lack of light.
  • In addition to blue and blue, sapphires also come in almost any color, these are the so-called multi-color or fancy varieties.
  • Today, Ceylon island is an actual source of high quality sapphires.
Sapphire Crystal

History

Blue and fancy sapphires have a long history. For thousands of years, this stone has decorated jewelry of the rulers and members of the clergy. Sapphire symbolized nobility, honesty and loyalty. Colors of all other blue gems were compared to their color. In ancient Greece and Rome, kings and queens were convinced that blue sapphires protected their owners from envy and evil. In the Middle Ages, the clergy wore these gems, symbolizing Heaven, and ordinary people thought that this gem attracted heavenly blessings. For centuries, the history of the stone was associated with romantic images. This association was strengthened in 1981, when British Prince Charles presented a blue sapphire wedding ring to Dianа Spencer. A second wave of his worldwide popularity began in 2010, when the same ring was donated by Prince William to his bride Kate Middleton.

Enhancement

The classic method of enhancement corundum mineral is heat treatment. About 90% of all mined sapphires are treated by this method. Many crystals and their fragments are heated before cutting. As a result of heating, some external properties (firstly, color characteristics) can be improved. The color of the stone may become more saturated, it is possible to lighten too dark colors or to remove unwanted shades (for example, violet or greenish), which reduce the price. During heating, some inclusions melt, and then clarity of a stone becomes better. Price of unheated sapphire can be approximately in 1.5-2 times higher than heated with the same characteristics. Among the treated sapphires, heated in the presence of titanium oxide is very common. In such diffusion samples, only the surface layer of a stone is colored in a brighter blue color. Cracky samples, filled with blue cobalt glass, have a very low price. Heating does not affect the hardness of corundum. It is important that natural origin without enhancement be confirmed by a certificate from a well-known gemological laboratory.

Sapphire properties

Photo

sapphire «Royal blue» from Sri Lanka

In the photo: precious stone sapphire «Royal blue» from Sri Lanka, 14.10 ct

The photo of unheated blue sapphire, Sri-Lanka, 9.18 ct

Precious light blue sample 5.60 ct from Ceylon

Precious light blue sample 5.60 ct from Ceylon

In the photo: Unique untreated stones over 30 ct each, Sri Lanka

Natural (untreated) Burmeese blue sapphire of the highest quality 5.23 ct

mineral crystals with uniform light color

Photo of corundum mineral crystals with uniform light color. Such form is typical for Sri Lankan origin

In the photo: the polychromic Ceylon stone

Video

Video of the sample of gem-quality faceted yellow corundum 7.22 ct.

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