Sapphire

 

CHEMISTRY: Al2O3
CRYSTALLOGRAPHY: Hexagonal
REFRACTIVE INDEX: 1.757 - 1.779
HARDNESS: 9
SPECIFIC GRAVITY: 3.99 - 4.0
CLEAVAGE: None
HEAT SENSITIVE: No
WEARABILITY: Excellent
SPECIAL CARE INSTRUCTIONS: None
ENHANCEMENTS: Heat treated. Common. Diffusion treatment, (places a thin blue coating on colorless sapphire.) Occasional. Irridation, (turns colorless gems yellow, orange or light blue.) 

The sapphire, together with the ruby, are members of the corundum group, which is the mineralogical name for aluminium oxide that crystallised into gemstones a long time ago as a result of pressure and heat at a great depth.  Pure corundum is colourless, but the presence of small amounts of other elements, especially iron and chrome, are responsible for giving sapphires their range of various colours: blues, reds, yellows, oranges, pinks, violets, greens.  Sapphires coloured red by the presence of chromic oxide are known as rubies.  Blue is the most commonly known sapphire colour and those not coloured blue are generally referred to as ‘fancies’.  Fancy sapphires are commonly referred to with the colour specified as a prefix to the word sapphire, for example, yellow sapphire, pink sapphire.
  

Parti sapphires are an exquisite Australian beauty!  The best examples are unique to Australia they contain both yellow and blue colours that then depending upon the facets, throw green!. Due to the natural blending of colours, Parti sapphires cannot be artificially manufactured and offer their owner a unique gemstone that is guaranteed natural.  No two parti sapphires are identical and each owner therefore has a truly individual gemstone.  A highly prized Parti sapphire is the "Pharoah's Eye".  The Pharoah's Eye is a blue crystal with a yellow core.  The gem is cut so the culet (bottom) of the stone is centred in the yellow core and the crown (top) is in the blue - this is a truly magnificent stone!!!

Star Sapphires have fine, needle-like inclusions called asterism. When these inclusions are numerous enough to make the stone translucent or opaque and are oriented properly, they allow light to be reflected in such a way that a moving star forms across the top of the stone. When a cutter recognizes this potential in a piece of rough sapphire, he will cut it in a dome shape. Stars are not visible in faceted stones.
 

Star sapphires occur when several tiny needle-like inclusions of rutile reflect light in a six point star-like figure.  Padparadja sapphires are characterised by an orange with a fine pink undertone, similar to that of a 'lotus flower' which its name depicts.

Sapphires were mined in prehistoric times with the oldest finds in Ceylon, or Sri Lanka as it is known today.  The most valuable sapphires are those from Kashmir, however, these mines now yield few stones.  Burmese sapphires are valued almost as highly and Ceylon sapphires are also well regarded.  Other important sources of sapphires are Thailand, Australia, Cambodia, Africa, Brazil, Montana and Colorado in the USA, with small quantities being found.

The term ‘Australian sapphire’ is used to denote darker coloured sapphires, whilst ‘Ceylon sapphire’ is used to denote pale to medium coloured sapphires

Today, many sapphires are heat treated to eliminate impurities and improve the gem’s colour and clarity.  

Sapphires vary widely in price depending on their size, colour, transparency, brilliance (affected by clarity and cutting) and their origin.  Sapphires are characterized by excellent hardness (Moh’s scale – 9) and are only exceeded in hardness by diamond.  For this reason, sapphires are very easy to look after and are common in everyday jewellery.  Ultimately, which is ‘the best’ sapphire is subjective and very much a personal preference.  Our advice to potential customers is to choose the stone that most appeals to you.

Sapphire is known as the wisdom stone, with each colour having its own particular wisdom.  Sapphire calms the mind, releases mental tension and confusion.  It stimulates concentration and facilitates self-expression.

Major Deposits and Characteristic Colors:

AFRICA:
Africa has numerous deposits of gem quality corundum and has recently been a source of new sapphire and ruby discoveries.

Tanzania:
UMBA River - Some blue, lavenders and purples to plums, yellows, golds to orange browns, pinks, and padparadschas.

SONGEA:
Deep red rubies, blues, blue greens, greens, yellows, pinks, alexandrite-type (blue in sunlight and fluorescent light, lavender to purple in incandescent).

TUNDURU:
Full spectrum of colors.

Madagascar:
Blue, very much like Sri Lankan blue. The rubies are clear red and often unheated. Range of pink from pale to intense.

Kenya:
LODWAR - Clear deep blue to very dark blue-green and an abundance of opaque blue stars.

GARBATULA:
deep, blackish blue-green to intense pleasant green.

ASIA:
Sri Lanka
The island nation south of India was known as Ceylon for many generations. Consequently "Ceylon-blue" is a color name outliving the change in national name. Sapphires of note in large sizes - over 5 carats - of outstanding color are predominantly of Sri Lankan origin. White, blue, purple, pink, yellow, gold, and padparadaschas.

Mysore (India)
Star rubies.

Myanmar (Burma)
Ruby and sapphire mines of Burma are legendary and have produced some of the world's finest rubies and blue sapphires.

MOGOK STONE TRACT:
Star rubies, star sapphires, rubies. Sapphire - violet, yellow, color-change, and blue.

MONGSHU:
Ruby.

TADJIKASTAN:
Ruby.

Thailand (Siam)
Thailand is a traditional supplier of sapphire and ruby. The majority of sapphire production from the Kanchanaburi field has been mined in the last ten years. This deposit is approaching depletion.

CHANTABURI:
blue, rubies, dark blue, green, yellow, and black star - 6 and 12 ray.

KANCHANABURI:blue and green, yellow and rubies.

Vietnam: Rubies and sapphires have been found in Vietnam since the late 1980's. They are very rarely seen in the jewelry market.

LUC YEN AND QUY CHAU:
red and red-pink rubies, hot pink and purple sapphire.

Cambodia:
PAILIN - blue sapphire and color change ruby.

AUSTRALIA:
Australia also has several deposits and contributes greatly to the sapphire jewelry market in mostly Inky blues to less known brilliant true blues, green, blue-green, yellow-green, yellows, oranges, and some pinks.

NORTH AMERICA:
Montana
Montana has four main deposits:

DRY COTTONWOOD CREEK:
yellow, gold and green, some pink, blue, and very, very rarely a ruby.

MISSOURI RIVER:
green, blue, yellow, orange, pink, and very rarely ruby.

ROCK CREEK:
full spectrum of colors including many bicolors, and also very rarely ruby.

YOGO GULCH:
blue and purple.