Ruby is one of the most coveted precious stones, and it is
ironical that impurities give it that brilliant red color.
You have undoubtedly used sandpaper for something or the other.
You may have also seen glittering red rubies set in eye-catching
gold ornaments. And if you haven’t seen a real ruby, you may have
seen pictures of it in glossy fashion magazines. Well, these two are
related. They share a common source – corundum a mineral form of
aluminum oxide (Al2O3).
Ruby, which is at its best when it is
pigeon-blood red in color, often varies in color from
cochineal to a pale rose-red. Sometimes it even has a tinge of
purple. Replacing a few aluminum atoms with chromium atoms
results in its brilliant red color.
The ratio of aluminum to chromium is
generally 1 to 5000. Ruby is characterized by high refractivity.
Cut and polished in the right way, it becomes a brilliant stone.
It has one peculiar feature. When it is
exposed to high temperature, it turns a lovely green. It,
however, regains its customary red after it cools down.
The natural form of
the shiny ruby is in bands of crystalline limestone. When cut in a
certain manner, some rubies exhibit a six-rayed star on the inside.
These stones are highly prized.
The area of origin can be named by the color of the ruby. For
example, rubies from Thailand are quite dark in color; those from
Myanmar are a better shade of red than those from Sri Lanka, and so
Ruby is a rare precious stone. Much of it is sourced from north
central Myanmar, Mandalay and parts of Thailand. The stone is
sometimes called Oriental ruby to distinguish it from other red
gems, which are red but not rubies. For instance, Cape rubies,
Australian rubies and Arizona rubies are fine garnets. Siberian ruby
is rubellite, red tourmaline, and balas ruby is ruby spinel.
Besides being used as jewelry, rubies are used in watches as
jeweled bearings and in the manufacture of scientific equipment.
The source mineral Corundum
Corundum is next only to the diamond as far as hardness
is concerned. Fine varieties of corundum give us the gemstones
sapphire and ruby and the less fine varieties have many industrial
uses. In its pure state, corundum is colorless.
Color is nothing but impurities in the stone. Chromium added to
corundum gives rubies the red color. The presence of iron and
titanium give us sparkling blue sapphires.
India, Russia, Zimbabwe and South Africa have rich deposits of
corundum. Its hardness has made it an industrially useful stone as
it can used for grinding optical glass and polishing metals. It is
also used to make sandpaper or what is also referred to as emery
The ever resourceful nature of man has successfully
explored the possibility of producing rubies artificially.
Artificial ruby is made by a procedure called the Verneuil process,
using purified ammonia alum and chrome alum. The coveted
pigeon-blood red has also been achieved to perfection by using
chromic oxide. Synthetic rubies contain the physical characteristics
of natural corundum. However, these can be easily distinguished by
microscopic bubbles and striae in it.