Sapphire

February 12, 2008

Nature, Precious Stones

gems, gemstones, precious stones, saphire, sapphire

The Blue Gemstone – Another Prince of Gems
I am sure you would like to know more about the gem stones.
This informative article is one of a series of 5 articles covering the four precious gemstones – Diamond, Ruby, Sapphire, Emerald and Pearls (which is really not a gem).

Which colour would you associate with Sapphire?
The answer is pretty obvious. Blue.

Most people believe that all sapphires are blue.
It is true that the best and most precious sapphires are blue.
But sapphires extend over a wide range of colours except red.

Sapphire is a form of Corundum

Chemically, sapphire is corundum, a crystalline form of aluminium oxide, found in nature as a mineral.
In this photograph, you can see a piece of natural corundum.
Corundum is the second hardest mineral on Earth (the hardest is diamond).

On the Mohs scale (which is a measure of hardness), the score of corundum is 9.
It is so hard that combined with other additives, it is used as an abrasive – from the common sand paper to large machine tools for machining anything from metals to the hardest stones.
Pure corundum is colourless.

Traces of other elements like chrome, iron, titanium or vanadium give it colour.
What is a Sapphire

Both sapphire and ruby are corundum, that is, aluminium oxide.
Their colours are different because of the presence of different trace elements.

A trace of chrome makes the gem red and it is called ruby.

Only red corundum can be called ruby.
Traces of iron, titanium or vanadium give the corundum different colours.

Corundum of all colours, other than red, are classified as sapphires.

Different kinds of Sapphires

Star Sapphires

Star sapphires contain intersecting needle-like inclusions (usually rutile, a mineral composed mainly of titanium dioxide ).When viewed under a single overhead light source, the sapphire will display a six-rayed ‘star’.
Blue sapphires
Deep and vivid blue sapphires are the most in demand.
Sapphire and India

The finest sapphire in the world, having the most intense and vivid blue hue (Kashmir Blue) originated from India’s north western region of Kashmir, along the Indo Pakistani border, in the Himalayas.

A landslide caused by an earthquake in the late 1800’s revealed sapphires in that region.

The region was excessively mined for eight years.

By the early 1900s, the region was completely depleted.

Where do the finest Sapphires come from
Sapphire and Ruby Mines of Mogok

After Kashmir, the world’s finest sapphires, rubies and spinels have been found in the Mogok Stone Tract of the high-altitude Mogok Valley, about 175 km northeast of Mandalay, in Myanmar (Burma).
The 4,800 square kilometer area, comprising the Mogok Valley, has over 1000 ruby and sapphire mines. In 1972, the world’s largest sapphire (63,000 carats) was found in the Mogkok valley.
But some of the finest sapphires have come from Sri Lanka.

Both the Logan sapphire and the Star of Bombay came from Sri Lanka.

Today, Madagascar is the world leader in sapphire production.

Some fabulous Sapphires

The 182 carat (36.4 g) Star of Bombay, is one of the world’s greatest blue star sapphire.
Douglas Fairbanks, Sr., the actor, gave it to his wife, the silent-film actress Mary Pickford.

It is now housed in the National Museum of Natural History, Washington D.C.
The massive 563.35 carat Star of India is the largest sapphire in the American Museum of Natural History.

But its colour is not deep, but a grayish blue.

The giant 423 carat Logan Sapphire set with 20 diamonds is the largest sapphire in the Smithsonian collection.

The stone has a rich blue color, but unfortunately is faceted with a large window.
Synthetic Corundum
Big and beautiful sapphires can be made artificially.

In 1903, Verneuil produced high quality synthetic corundums on a commercial scale by using a flame fusion process.

This simple and inexpensive process is used to produce flawless single crystal sapphires, rubies and other corundum gems of much larger size than are normally found in nature.

The Verneuil Process has been replaced by the Flux-Grown method which produces large, high-quality gem-grade sapphire.
Synthetic sapphire crystals of large size, up to many inches in diameter, can be grown in cylindrical crystal boules.

On the right, you can see a ring with a synthetic star sapphire.
Improvements
Natural sapphires are usually heat treated to improve their appearance and color.

Heat treatment improves the sapphire’s color and clarity.

Many natural sapphires are also diffusion treated.

In this process, trace elements are added to impart or to improve colors.
The sapphire is a prized possession.

A sapphire which suits its owner is supposed to bring very good luck.

And a sapphire which does not suit its owner could bring extreme misfortune.

Prospective purchasers often test its suitability by keeping it under their pillow.

Good dreams mean it is suitable for them.

Bad dreams indicate that they should not purchase the sapphire.