Inorganic Gemstones

Sapphire

8.41 carat blue star sapphire from Mogok (Burma).

All gem-quality corundum that isn't red is known as sapphire, yet this name is popularly linked to the colour blue. Variation in colour, because of iron and titanium impurities, spans many shades, however the best is really a clear, deep blue. Some stones, called “colour-change sapphire”, exhibit different shades of blue in artificial and sun light.

Top quality sapphire can be found in Burma, Sri Lanka, and India. The very best Indian Sapphire is cornflower blue, and present in Kashmir, either in pegmatites or as waterworn pebbles in alluvial deposits. Sapphire from Thailand, Australia, and Nigeria is dark blue, and could appear nearly black. Montana (USA) produces sapphire of the attractive metallic blue. Other localities include Cambodia, Brazil, Kenya, Malawi, and Colombia.

Synthetic sapphire production began within the late 1800s. Commercial quantities became available in early 20th century.


Properties
Chemical Composition: 
Aluminium Oxide - Al2O3 (trace elements Chromium, Iron, Titanium, etc. are responsible for the different colored varieties.
Classification / Type: 
-
Colors / Varieties: 
  • White Sapphire
  • Blue Sapphire
  • Pink Sapphire
  • Green Sapphire
  • Yellow Sapphire
  • Pink-Orange Sapphire (Padparadscha)
  • Phenomenal
    • Color Changing Sapphire
    • 6-Ray Star Sapphire
    • Parti-colored Sapphire
    • Trapiche Sapphire
Crystal System / Forms: 
Trigonal System
Hardness: 
9
Specific Gravity: 
3.98 - 4.00
Cleavage / Fracture: 
None may show parting / Conchoidal fracture. (Parting or false cleavage occurs along directions of weakness which are parallel to the basal plane or the rhombohedral faces of the crystal and are observed externally as grooves or striations on the surface.
Optic Character: 
Anisotropic, D.R., Uniaxial negative
Lustre: 
Vitreous
Refractive Index / Birefringence: 
1.762 - 1.770 / 0.008; Range: 1.754 - 1.778
Pleochroism: 
Strong in deep colored varieties
Dispersion: 
0.018
Magnification: 
  • Crystals of calcite, dolomite, apatite, etc.
  • Silk - three directional needles of rutile intersecting at 60° / 120°; Needles of boehmite intersecting at almost 90°; Needles of ilmenite etc.
  • Parallel polysynthetic twin lamellae.
  • Color zoning and angular growth zoning.
  • Fingerprints and fluid inclusions.
  • Zircon halo inclusions etc.
U.V. Fluorescence: 
Varies according to the color.
Spectrum: 
Blue, green, brown and yellow sapphires: shows a three band absorption in the blue at 450nm, 460nm and 470nm. Generally at least one of these bands is present.
Cause of Color: 
  • Blue Sapphire: Traces of Iron and Titanium.
  • Green / Yellow Sapphire: Traces of Iron (Fe2+ / Fe3+).
  • Color Changing Sapphire: Traces of Chromium and Vanadium.
Treatment (Enhancement): 
Specific Tests & Remarks: 
-
Synthesis: 
Simulants (with key separation tests): 
  • Blue Sapphire: Tanzanite (optic figure, pleochroism, R.I., S.G.), Natural / Synthetic Spinel (optic character, pleochroism, R.I., spectrum, S.G.), Benitoite (dispersion, doubling), Iolite (optic figure, pleochroism, R.I., S.G.), Kyanite (optic figure, R.I., S.G., inclusions), Synthetic Quartz (optic figure, R.I., S.G.), Glass (optic character, inclusions), Doublets (inclusions, U.V. fluorescence).
  • Yellow Sapphire: Chrysoberyl (optic figure, spectrum, inclusions), Citrine (optic figure, R.I., S.G., inclusions), Topaz (optic figure, R.I., S.G.), Yellow Beryl (R.I., S.G., inclusions), Hessonite Garnet (optic character, inclusions), Sillimanite (optic figure, inclusions, R.I., S.G.), Synthetic Cubic Zirconia (dispersion, S.G., U.V. fluorescence), etc.
Geological Occurrence: 
In igneous and metamorphic rocks (marble, dolomite, etc.
Sources: 
India (from Kashmir as Kashmiri Sapphire, Karnataka, Orissa), Myanmar (known as Burmese Sapphire), Thailand, Sri Lanka, Australia, Africa (Tanzania, Nigeria, Kenya, Madagascar), U.S.A. (Montana), Cambodia (Pailin).
Cuts & Uses: 
Facetted cuts (usually mixed cuts), cabochons, beads, carvings, etc.

Did you know?

Jewellery is one of the most bought products online. An estimated $1 billion USD of diamonds are bought annually via the Internet. Over 40 million people use the Internet to trade!

In Germany, the garland of ambers is hung around the necks of the infants, so that their teeth might come out without much trouble.

In Turkey, people fix a piece of amber in the hubble-bubble, dogged by an age old belief that the presence of the jewel would destroy all the germs and no disease would spread, even after many have dragged their puffs from it.

In Greece, people think if wine is poured into the cups made of amethyst, one does not get drunk after drinking that.

In Rome, a talisman having coral pieces is considered very auspicious to quell the bad spells of evil look. The Romans were in the habit of hanging chains made of ancient coral pieces from the cradle of the infants to protect them from evil effects.

In China, people wear rings studded with tiny conch or oyster shells as they believe it cures all aches such as stomach ache, worms and like.

In India, pendants made of silver and studded with pearls are hung from the necks of the children to save them from any bad effects.

Greeks still believe, if women wear blue sapphires then no sense of immorality would pollute their mind nor can any fear of the supernatural can trouble them.

The Pope Innocent III had circulated an order asking all the priests wear blue sapphire, so that morality can be strengthened.

It is said about turquoise, that when the stone changes its color into yellow, it actually signals bad times to the person who wears it.

It is believed that a turquoise gifted to a friend or a lover turns his or her life into one of happiness and good luck.

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