Difference between revisions of "Spinel"

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[[Image:Badak1.JPG|left|framed|Spinel from Badak, Afghanistan]] <br clear="left" />
 
[[Image:Badak1.JPG|left|framed|Spinel from Badak, Afghanistan]] <br clear="left" />
  
Spinel is a mineral species.  For many centuries, most gem spinels were misidentified as [[sapphire]] or [[ruby]] because they have similar properties and occur in the same geological deposits. The two inch "ruby" in the center of the British Imperial Crown was only recently identified as a spinel! Spinels also occur in a vast array of colors. They are slightly softer than sapphires but still very durable. The earliest spinels, used as ornaments were found in Buddhist tombs in Afghanistan. Blue spinels have been found in England, dating back to the Roman occupation (51 BC to 400 AD).<br><br>
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Spinel is a mineral species.  For many centuries, most gem spinels were misidentified as [[sapphire]] or [[ruby]] because they have similar properties and occur in the same geological deposits. The two inch "ruby" in the center of the British Imperial Crown was only recently identified as a spinel! Spinels also occur in a vast array of colors. They are slightly softer than sapphires but still very durable.<br>The earliest known use of spinels was as ornaments found in Buddhist tombs in Afghanistan. Blue spinels have been found in England, dating back to the Roman occupation (51 BC to 400 AD).

Revision as of 19:53, 23 December 2006

Spinel
Chemical composition Mg(Al2O4) Magnesium aluminum oxide
Crystal system Cubic
Habit Octahedral, contact twins
Cleavage Imperfect
Fracture Conchoidal, uneven
Hardness 8
Optic nature Isotropic
Refractive index 1.712 - 1.736
Birefringence None
Dispersion 0.026
Specific gravity 3.58 - 3.61
Lustre Vitreous
Pleochroism None
Spinel from Badak, Afghanistan

Spinel is a mineral species. For many centuries, most gem spinels were misidentified as sapphire or ruby because they have similar properties and occur in the same geological deposits. The two inch "ruby" in the center of the British Imperial Crown was only recently identified as a spinel! Spinels also occur in a vast array of colors. They are slightly softer than sapphires but still very durable.
The earliest known use of spinels was as ornaments found in Buddhist tombs in Afghanistan. Blue spinels have been found in England, dating back to the Roman occupation (51 BC to 400 AD).