Corundum (from Tamil kurundam) is a crystalline form of aluminium oxide and one of the rock-forming minerals. It is naturally clear, but can have different colors when impurities are present.
Corundum
Chemical composition -- Aluminum oxide.
Color -- almost all colors. Medium to dark red stones are known as ruby; other colors, sapphire.
Ch. 7: Corundum: Sapphire Rubies etc.
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66 PRECIOUS STONES.
Corundum is crystalline aluminum oxide, Al2O3, second hardest on Mohs Scale, and one of the most popular (and expensive) of gem minerals. Ruby is red corundum; all other colors are Sapphire.
Corundum crystallizes in the trigonal structure and is most often found as tabular hexagonal crystals (ruby) and hexagonal bipyramids (sapphire) although other habits may be encountered as well. Twinning is quite common.
Corundum comes in many colors
(Photo by ICA/Bart Curren)
In this text, rubies include all corundum with a red hue predominant; sapphires include all the corundum of all other hues. Nevertheless a world wide debate rages about the definition of ruby.
CORUNDUM:
A mineral that forms rubies and sapphires.
See also: Emerald Ruby Gemstones
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Sapphire corundum has no cleavage planes, but does have a conchoidal fracture, and can be parted more easily in certain directions.
Diamond and Corundum. A chemist would call a true mineral a pure substance, just as sugar and salt are pure substances to the chemist. Thus diamond is a "mineral species," as is also corundum.
Usage: Due to corundum's hardness, it is commonly used in as an abrasive in machining, from huge machines to sandpaper. Corundum that has been synthetically manufactured from bauxite is most often used for this purpose.
Associations:
Gem quality corundum comes from metamorphed limestone or dolostone (needs high Al concentrations, here presumably from detrital deposits) ...
corundum
Corundum (aluminum oxide Al2O3) is the hardest mineral other than diamond, though only 1/140 as hard. Red corundum is ruby, other colors are called sapphires.
Corundum was first synthesized in the early 1900's by a simple flame fusion process.
Corundum
See our:
blue corundum jewelry (sapphire) or red corundum jewelry (ruby).
A mineral (aluminium oxide) that is the hardest mineral other than the diamond; its hardness on the Mohs scale is 9.
Corundum
A gem mineral of crystallized aluminum and oxygen. Ruby and sapphire are the most valuable corundum.
Crystal ...
Corundum
A mineral. A red corundum is a ruby by definition. Any other color is a sapphire, which occur in every color.
Corundum A crystalline form of aluminum oxide known in the gemstone world as ruby and sapphire. It is naturally clear, but can have different colors when impurities are present.
CORUNDUM. Crystallised alumina--rubies, sapphire, etc.
CRADLE. Trough in which, by a rocking motion, placer miners wash auriferous or gem gravels.
CRYSTALLOGRAPHY. The science which describes or delineates the form of crystals.
CORUNDUM
Corundum is a very hard mineral (hardness 9); only diamond is harder. Corundum is called ruby or sapphire, depending on the color (which depends on which metallic oxides are present).
Corundum: Gemstone species of good hardness and durability of which the red variety is ruby and all other colours are sapphire.
Corundum
Corundum is a hard mineral that exists in the form of colored crystals, such as Rubies and Sapphires.
Crown ...
corundum Ruby and sapphire which is number nine on the Mohs hardness scale.
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counter-weight Used in the mechanical style carat balance scales.
Corundum
Very hard rock forming mineral group that contains the gems Sapphire and Ruby. If the corundum is red it is labeled as a ruby, all other colours are sapphires.
Crystal ...
Corundum: The name of a family of stones composed of crystallized aluminum and oxygen that includes rubies and sapphires. The color of these stones depends on the oxides present in their composition.
corundum
A mineral that comes in several colours including ruby and sapphire, depending on the metallic oxides that it contains. Corundum that does not contain any oxides is colourless and known as pure corundum or white sapphire.
Corundum
Group of minerals that includes Rubies and Sapphires.
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The Corundum Family: Ruby, Sapphire
Diamonds
The Quartz Family: Amethyst, Citrine and Agates ...
The new corundum collection contains representative samples from all major sapphire-producing regions.
Corundum is found in many colors besides red (ruby) and blue (sapphire). Colorless, yellow, violet, green and even brown colors may be found.
Corundum (sapphires) comes in all color types. Blue Corundum is called Blue Sapphire; Pink Corundum is called Pink Sapphire, etc.
corundum (n) corundum is a mineral which, when transparent, forms the gemstones ruby and sapphire. Red (or pink) variants are ruby, all other colours are sapphire. Corundum has a Mohs hardness of 9.
Corundum
10
Diamond
To identify minerals in the field even if you don't have a complete set of the minerals of hardness on hand (which most people won't), use the scratch-test to get a rough guess of hardness.
Corundum
Precious stones, most common used are blue Sapphire and red Ruby. Consist of Aluminum oxide. Avaialble in many different colors.
Hardness : 9 Refractive Index : 1.762- 1.770 Density : 3.97-4.03 ...
CORUNDUM - (Sapphire variety)
Loch Scridain, Isle of Mull.
A 2 mm embedded crystal.
SCOLECITE - Ben More, Isle of Mull.
Parallel-growing, elongated, unterminated crystal group
to 40mms on volcanic matrix.
Corundum
A mineral species of which sapphire and rubies are members
Costume jewelry ...
Corundum manifests itself in two forms of gemstone - Rubies and Sapphires. Part of the same family, the color of these gems depends on the metallic oxides present in their composition.
Corundum - The mineral composition that makes up the ruby and sapphire family of gemstones.
Crown - The upper facets of the diamond, above the girdle, leading up to the table.
Corundum in any other color is a sapphire,
which can be the familiar blue, or
many other brilliant colors -
but only red corundum is a ruby.
Many rubies are heat treated
to enhance their color.
CORUNDUM A gem species that is found in many colors. Red Corundum is called Ruby and all other varieties are called Sapphire. Blue Sapphire is best known, however Pink Sapphire, Green Sapphire, and Yellow Sapphire are also relatively popular.
Corundum is called ruby or sapphire, depending on the color which depends on which metallic oxides are present: Rubies contain chromic oxide, blue sapphires contain titanium, yellow sapphires contain ferric oxide.
corundum
The mineral name corundum is not well-known to many, but its two gem varieties, ruby and sapphire are. In its purest form, corundum is colorless. It is a combination of aluminum and oxygen (Al2O3) and belongs to the trigonal crystal system.
Corundum: The crystalline form of aluminum oxide it is an extremely hard [second only to diamonds] rock forming mineral. This family includes sapphires and rubies. The stones color depends on the amount of metallic oxide present.
RBY227, Corundum, Ruby, 'AA', [H], 5.0x3.1mm Emerald Cut, 0.28 ct. $ 356.00
RBY191, Ruby, Ruby, [E], 4.6mm Trillion Cut, 0.90 ctw. $ 1334.99 pair
Indian Star Ruby ...
Ruby - a corundum with the Mohs' rating of 9, making it the hardest mineral after diamond. Ruby has no cleavage but has preferred directions of parting. Inclusions are common and not an indication of lower quality.
Sapphire (Corundum Family)
Sapphire is a most precious and valuable blue gemstone and very desirable due to its excellent colour, hardness, durability, and lustre.
A variety of corundum, like ruby and sapphire, which could be considered a precious stone as it is, in reality, an orange sapphire. It is virtually unknown to the vast majority of people and can therefore be purchased at a reasonable price.
Sapphire: Any corundum other than ruby, but generally referring to the blue variety. Other colors are pink sapphire, purple sapphire, green sapphire, etc.
Variety of the Corundum Species
Formed in metamorphic and igneous rocks
Color: Varieties of red
Hardness: 9
Transparency: Transparent to opaque
The most sought after color of the ruby is pure red with a touch of blood, a.k.a. "pigeon's blood" ...
A member of the corundum family of gems, the ruby is a red, clear stone. Known as the "king of gems" the ruby is second only in value to diamond (exceptional specimens surpass diamonds in value).
The mineral name Corundum comes from Sanskrit "kuruntam", "red-stone or ruby". The name Ruby comes from the Latin "ruber", meaning "red". The name Sapphire comes from the Sanskrit "sanipriya", which means "dear to the planet Saturn".
The second major corundum zone is found behind the granite mountain of Khao Sabab, which dominates the view from Chanthaburi. These mines are right on the border between Chanthaburi and Trat Provinces, and include: ...
A gemstone of the corundum family, although blue is the color most commonly associated with sapphires, they come in a range of colors from white to orange to green to pink.
Ruby
Ruby is a corundum that vary in color from red to purple to pink to brown. Diamonds are the only precious stones that are harder than rubies. Rubies are extremely valuable.
see Corundum
Adamite
zinc arsenate: Zn2(AsO4)(OH)
Crystallography: orthorhombic, drusy crust of short prismatic or horizontally elongated crystals ...
Also referred to as Bio Lemon Black Star Sapphire:A black sapphire formed from corundum with Titanium and Iron impurities.
Can be stone studded RubyA precious gemstone, and a member of the corundum family, rubies are always, by definition, red, but be aware that many other red gemstones and imitations might be assumed to be a ruby.
Ruby, like sapphire, is a variety of corundum and only exists as a true red in color. The finest color is a vivid, almost pure spectral red with a very faint undertone of blue, as seen in Burmese rubies which are considered the finest.
A member of the Corundum family. DARK BLUE SAPPHIRE inspires creative expression, intuition and meditation. GREEN SAPPHIRE brings luck. ORANGE SAPPHIRE, also known as Padparadschah, augments wisdom, optimism and friendliness.
Rubies are precious stones and a member of the corundum family (Al2O3). Rubies range in color from the classic deep red to pink to purple to brown. Rubies are extremely hard; only diamonds are harder.
The red variety of corundum. Long cherished for their deep passionate color, rubies are available as natural gemstones, but also are widely available as lab created gemstones. Rubies are also sometimes cut into cabochons. Ruby is the July birthstone.
 See also: Stone, Color, Sapphire, Gemstone, Mineral
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