Corundum

Al 2 O 3 C'''orundumcorindoncorundum structuresapphire
Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium.wikipedia
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Sapphire

sapphire crystalstar sapphireBlue sapphire
Corundum has two primary gem varieties: ruby and sapphire. In 1847, Ebelmen made white synthetic sapphires by reacting alumina in boric acid.
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminum oxide with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium.

Ruby

rubiessynthetic rubyR'''uby
Corundum has two primary gem varieties: ruby and sapphire.
A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide).

Chromium

Crchromechromium(III)
Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium.
Its Mohs hardness is 8.5, which means that it can scratch samples of quartz and topaz, but can be scratched by corundum.

Mohs scale of mineral hardness

Mohs hardnessMohs scalehardness
Because of corundum's hardness (pure corundum is defined to have 9.0 on the Mohs scale), it can scratch almost every other mineral.
For example, corundum (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum.

Emery (rock)

emeryemery powderemery grinder
Some emery is a mix of corundum and other substances, and the mix is less abrasive, with an average Mohs hardness of 8.0. Emery-grade corundum is found on the Greek island of Naxos and near Peekskill, New York, US.
It largely consists of corundum (aluminium oxide), mixed with other minerals such as the iron-bearing spinels, hercynite, and magnetite, and also rutile (titania).

Mineral

mineralsmineral depositsaccessory mineral
It is a rock-forming mineral.
Gem minerals are often present in several varieties, and so one mineral can account for several different gemstones; for example, ruby and sapphire are both corundum, Al 2 O 3.

Abrasive

abrasivesbonded abrasiveabrasion
It is commonly used as an abrasive on everything from sandpaper to large tools used in machining metals, plastics, and wood.
(While useful for comparative purposes, the Mohs scale is of limited value to materials engineers as it is an arbitrary, ordinal, irregular scale.) Diamond, a common abrasive, for instance occurs both naturally and is industrially produced, as is corundum which occurs naturally but which is nowadays more commonly manufactured from bauxite.

Titanium

Tititanium oretitanian
Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium.
Also known is Ti 2 O 3, with the corundum structure, and TiO, with the rock salt structure, although often nonstoichiometric.

Crystal

crystallinecrystalscrystalline solid
Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium.
Likewise, the only difference between ruby and sapphire is the type of impurities present in a corundum crystal.

Aluminium

aluminumAlall-metal
In addition to its hardness, corundum has a density of, which is unusually high for a transparent mineral composed of the low-atomic mass elements aluminium and oxygen.
It can be found in nature in the mineral corundum, α-alumina; there is also a γ-alumina phase.

Vanadium

Vvanadium steelV 3 Si
Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium.
Vanadium oxide can be used to induce color centers in corundum to create simulated alexandrite jewelry, although alexandrite in nature is a chrysoberyl.

Naxos

NaxiansNaxos IslandNaxos, Greece
Emery-grade corundum is found on the Greek island of Naxos and near Peekskill, New York, US.
The island is famous as a source of emery, a rock rich in corundum, which until modern time was one of the best abrasives available.

Aluminium oxide

aluminaaluminum oxideAl 2 O 3
Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium. Frimy and Auguste Verneuil manufactured artificial ruby by fusing [[Barium fluoride|]] and [[aluminium oxide|]] with a little chromium at temperatures above 2000 C. In 1903, Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process. In 1847, Ebelmen made white synthetic sapphires by reacting alumina in boric acid.
It occurs naturally in its crystalline polymorphic phase α-Al 2 O 3 as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire.

Verneuil process

flame fusionVerneuila process
Frimy and Auguste Verneuil manufactured artificial ruby by fusing [[Barium fluoride|]] and [[aluminium oxide|]] with a little chromium at temperatures above 2000 C. In 1903, Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process.
It is primarily used to produce the ruby and sapphire varieties of corundum, as well as the diamond simulants rutile and strontium titanate.

Oxygen

OO 2 molecular oxygen
In addition to its hardness, corundum has a density of, which is unusually high for a transparent mineral composed of the low-atomic mass elements aluminium and oxygen.
The Earth's crustal rock is composed in large part of oxides of silicon (silica, as found in granite and quartz), aluminium (aluminium oxide, in bauxite and corundum), iron (iron(III) oxide, in hematite and rust), and calcium carbonate (in limestone).

Igneous rock

igneousigneous rocksdecompression melting
It also occurs in low silica igneous syenite and nepheline syenite intrusives.
The completed rock analysis is first to be interpreted in terms of the rock-forming minerals which might be expected to be formed when the magma crystallizes, e.g., quartz feldspars, olivine, akermannite, Feldspathoids, magnetite, corundum, and so on, and the rocks are divided into groups strictly according to the relative proportion of these minerals to one another.

Auguste Victor Louis Verneuil

Auguste VerneuilVerneuil method
Frimy and Auguste Verneuil manufactured artificial ruby by fusing [[Barium fluoride|]] and [[aluminium oxide|]] with a little chromium at temperatures above 2000 C. In 1903, Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process.
In 1902 he discovered the "flame fusion" process, today called the Verneuil process, which remains in use today as an inexpensive means of making artificial corundum, or rubies and sapphires.

Jacques-Joseph Ebelmen

Ebelmen
In 1847, Ebelmen made white synthetic sapphires by reacting alumina in boric acid.
In 1836 he was sent to Vesoul as a mining engineer, and began studying the different ores at Franche-Comté, where his reputation grew, growing artificial crystals of a number of minerals including corundum, chrysoberyl and peridot.

Hematite

haematitehematitichaematite iron ore
Hematite forms in the shape of crystals through the rhombohedral lattice system, and it has the same crystal structure as ilmenite and corundum.

Craigmont, Ontario

Craigmont
Historically it was mined from deposits associated with dunites in North Carolina, US and from a nepheline syenite in Craigmont, Ontario.
It was a former mining town that produced corundum from deposits in Mount Robillard, directly north of the community.

Pegmatite

pegmatitespegmatiticpegmatitic veins
Other occurrences are as masses adjacent to ultramafic intrusives, associated with lamprophyre dikes and as large crystals in pegmatites.
Pegmatites are important because they often contain rare earth minerals and gemstones, such as aquamarine, tourmaline, topaz, fluorite, apatite and corundum, often along with tin and tungsten minerals, among others.

Laser

laserslaser beamlaser light
Apart from ornamental uses, synthetic corundum is also used to produce mechanical parts (tubes, rods, bearings, and other machined parts), scratch-resistant optics, scratch-resistant watch crystals, instrument windows for satellites and spacecraft (because of its transparency in the ultraviolet to infrared range), and laser components.
For example, the first working laser was a ruby laser, made from ruby (chromium-doped corundum).

Hexagonal crystal family

Trigonalhexagonalrhombohedral
Corundum crystallizes with trigonal symmetry in the space group Rc and has the lattice parameters a = 4.75 Å and c = 12.982 Å at standard conditions.

Watch

wristwatchwatcheswristwatches
Apart from ornamental uses, synthetic corundum is also used to produce mechanical parts (tubes, rods, bearings, and other machined parts), scratch-resistant optics, scratch-resistant watch crystals, instrument windows for satellites and spacecraft (because of its transparency in the ultraviolet to infrared range), and laser components.
Some are made entirely of faceted sapphire (corundum).

Iron

FeFe 2+ Fe(III)
Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium.