Difference between revisions of "Sapphire"

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(Sapphire history)
(Sapphire history)
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[[Image:7894a_d.jpg|left|thumb|250px|Unheated Padparadscha Sapphire, 3.96 ct <br /> Photo by Jeff Scovil<br />Courtesy of R.W. Wise Goldsmiths]]<br clear />
 
[[Image:7894a_d.jpg|left|thumb|250px|Unheated Padparadscha Sapphire, 3.96 ct <br /> Photo by Jeff Scovil<br />Courtesy of R.W. Wise Goldsmiths]]<br clear />
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.
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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.<br clear="left" />
  
 
==Diagnostics==
 
==Diagnostics==

Revision as of 07:50, 10 April 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

Unheated Padparadscha Sapphire, 3.96 ct
Photo by Jeff Scovil
Courtesy of R.W. Wise Goldsmiths

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

Un-heated Sapphires

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 un-treated Burmese blue sapphire.
Photo courtesy of Apsara.co.uk
Rounded guest crystals, possibly calcite, in an un-treated Burmese blue sapphire.
Photo courtesy of Apsara.co.uk
Un-dissolved rutile silk in an un-treated Sri Lankan blue sapphire. Iridescent colours can be seen when this inclusion is viewed using a fibre optic light.
Photo courtesy of Apsara.co.uk


Heated Sapphires

Microscopic particle inclusions with straight colour banding in a heat treated Thai blue sapphire. The particles give the stone a sleepy or hazy appearance which is common to sapphires from Kanchanaburi, Thailand.
Photo courtesy of Apsara.co.uk



Beryllium-Treated Sapphires

Dendritic inclusion with 'cotton wool' type inclusions in beryllium-treated sapphire.
Photo courtesy of Apsara.co.uk
Liquid tubular channel inclusions in beryllium-treated sapphire.
Photo courtesy of Apsara.co.uk
Wheat-like feather inclusion in beryllium-treated sapphire.
Photo courtesy of Apsara.co.uk


A cross-sectioned slice through a beryllium-treated sapphire. The orange colour rim is clearly visible around the pink core.
Photo courtesy of Apsara.co.uk


Sapphire mining

Kashmir, Burma, Sri Lanka, Madagascar, Australia, China, Montana USA, Thailand

Sources

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