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sapphire information
Sapphire Gemstones
Sapphire (from Hebrew:
Sapir) is the single-crystal form
of aluminium
oxide (Al2O3), a mineral known as corundum.
It can be found naturally as gemstones or
manufactured in large crystal boules for
varied applications, including infrared optical
components, watch faces, high-durability windows, and wafers for
the deposition of semiconductors such as GaN nanorods.
The corundum group consists of pure aluminium oxide. Trace amounts of other elements
such as iron, titanium and chromium give
sapphires their blue, yellow, pink, purple, orange or greenish color. Sapphire
includes any gemstone quality varieties of the mineral corundum except the fully
saturated red variety, which is instead known as ruby.
What is Sapphire?
Sapphire is the non-red variety of corundum, the second hardest natural mineral
known to mankind. The red variety of corundum is Ruby - all other colors are
called sapphire. Sapphires are well known among the general public as being
blue, but can be nearly any color, even colorless. White (or colorless but
massive) sapphire would more properly be called corundum. The blue color is
by far the most popular color for sapphire but orange-pink, golden, white,
and even black have generated much interest in the gem trade. Oriented rutile
crystal inclusions cause a six-pointed-star light effect (called asterism to
form the popular Star Sapphire.
Many of the finest watches have crystal faces made of artificial sapphire - these are extremely durable and scratch resistant.
One interesting bit of trivia - sapphire is aluminum oxide, and aluminum is a highly reactive metal. Any freshly exposed surface of aluminum is quickly oxidized to corundum (sapphire), so it can be said that your lawn chair (or screen door, or any other aluminum object) is coated with sapphire.
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What makes a gemstone?
Generally speaking, a gemstone is a stone that is beautiful, rare, and durable
(resistant to abrasion, fracturing and chemical reactions). Some minerals can
be very beautiful, but they may be too soft and will scratch easily (such as
the mineral fluorite). Fluorite is extremely colorful and pretty but has a
hardness of only 4 on the Moh's hardness scale and has four perfect cleavage
directions, which makes it only an oddity as a cut gem. Others are too common
and are given a semi-precious status (such as agate). Most gemstones have good
hardness (above 5) and a high index of refraction (the higher the index of
refraction the greater the sparkle). All gemstones have some characteristics
falling short of perfection though; even the seemingly perfect Diamond has
four directions of cleavage.
Most gems are silicates which can be very stable, hard minerals. A few gems are oxides and only one gem, diamond, is composed of a single element, carbon. There are also a few gemstones that are not true minerals (called mineraloids) but are included here: opal, amber, and moldavite. While almost any mineral can be cut in the manner of a gemstone, below is a list of some of the gem kingdom's more prized and recognized members:
Additional information:
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