Difference between revisions of "Sapphire"

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[[image:Microscopic_particle_inclusions_with_straight_colour_banding_in_heat-treated_Thai_blue_sapphire.jpg|thumb|left|240px|Microscopic  particle inclusions with straight colour banding in a heat treated Thai blue sapphire.<br>Photo courtesy of Apsara.co.uk]]
 
[[image:Microscopic_particle_inclusions_with_straight_colour_banding_in_heat-treated_Thai_blue_sapphire.jpg|thumb|left|240px|Microscopic  particle inclusions with straight colour banding in a heat treated Thai blue sapphire.<br>Photo courtesy of Apsara.co.uk]]
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==Sapphire mining==
 
==Sapphire mining==

Revision as of 13:49, 24 March 2007

Sapphire
Chemical composition Al2O3
Crystal system Trigonal
Habit Prismatic, tabular
Cleavage None, may show parting on twinned stones
Fracture Conchoidal
Hardness 9
Optic nature Uniaxial -
Refractive index 1.762-1.770
(+.009,-.005)
Birefringence 0.008-0.010
Dispersion Low, 0.018
Specific gravity 4
Lustre Vitreous
Pleochroism Moderate to Strong
Cornflower Ceylon sapphire


Sapphire is an aluminum oxide occurring in every color of the rainbow. When it is red, it is termed ruby. It is a stone of great hardness and durability. It can also have phenomenal characteristics like asterism (star sapphire) and color changing (like alexandrite). The color changing varieties are mesmerizing, having the ability to change color depending on whether they are viewed in daylight or incandescent light.

Sapphire history

The name is derived from the Greek word "sappheiros" meaning "blue". The history of sapphire dates back to at least the 7th century BC, when they were used by the Etruscans. The sapphires used by the Etruscans, Greeks and Romans were imported from India (what is now Sri Lanka). Sapphires were reputed to protect kings from harm and envy. In the 13th century, it was written that sapphires had the power to protect against poverty, to make a stupid man wise and an irritable man good-tempered.

Diagnostics

Spectrum

Spectrum of blue, green and Australian yellow sapphire (high iron content).

Natural blue, green and yellow sapphires with a high iron content may show the typical "450 complex" as seen in this image. The clear lines at 450 and 460nm (less sharp than the 450nm line) will be accomanied with a third (sometimes faint) line at 470nm. Due to partial absorption of wavelengths between these 450 and 460nm lines, this whole section may blend together with "smudges" between the lines.
With lesser iron content only the 450nm line may be observed in natural blue and yellow sapphire. Although this same 450nm line can also be observed in some blue flame fusion (Verneuil) synthetic sapphire, the "450 complex" will never be seen in synthetic sapphire.

Phenomena

Asterism

12 ray star sapphire
Photo courtesy of
Wild Fish Gems

Color change

Under daylight
Photo courtesy of The Gem Trader
Under incandescent light
Photo courtesy of The Gem Trader


Cat's eyes

Trapiche

Inclusion Images

Distorted guest crystal (possibly calcite) in an un-treated Burmese pink sapphire.
Photo courtesy of Apsara.co.uk
Silk and guest crystals in an un-treated Burmese pink sapphire.
Photo courtesy of Apsara.co.uk
Unusual cluster of rutile silk in an un-treated Madagascan pink sapphire.
Photo courtesy of Apsara.co.uk


Calcite guest crystal in an un-treated Madagascan pink sapphire.
Photo courtesy of Apsara.co.uk
Guest crystals in an un-treated Sri Lankan blue star sapphire. Fine rutile silk can be faintly seen in the background.
Photo courtesy of Apsara.co.uk
A multitude of guest crystals in an un-treated Burmese blue star sapphire.
Photo courtesy of Apsara.co.uk


Calcite guest crystals in an un-treated Burmese blue sapphire.
Photo courtesy of Apsara.co.uk
Liquid fingerprint inclusion in an un-treated Burmese blue sapphire.
Photo courtesy of Apsara.co.uk
Calcite guest crystals in an un-treated Burmese blue sapphire.
Photo courtesy of Apsara.co.uk


Liquid fingerprints, guest crystals and two phase inclusions in an untreated Burmese blue sapphire.
Photo courtesy of Apsara.co.uk
Rounded guest crystals, possibly calcite, in an untreated Burmese blue sapphire.
Photo courtesy of Apsara.co.uk
Un-dissolved rutile sile in an untreated Sri Lankan blue sapphire
Photo courtesy of Apsara.co.uk


Microscopic particle inclusions with straight colour banding in a heat treated Thai blue sapphire.
Photo courtesy of Apsara.co.uk


Sapphire mining

Kashmir, Burma, Sri Lanka, Madagascar, Australian, China

Sources

  • A students' guide to spectroscopy (2003) - Colin H. Winter