Sapphires
and rubies are both members of the
corundum family with the same hexagonal
crystallographic structure. The
basic chemical formula is AL22O3
.. the same for both ruby and sapphire.
It is the presence of trace elements
like chromium, iron, vanadium and
titanium which are responsible for
the wide range of colors in which
the mineral occurs. When a corundum
is red, it is known as a ruby and
any other color is a sapphire. In
practice however, the determination
is not always so straightforward
because there are no internationally
accepted standards for the color
of a ruby. Gemologists could describe
the same stone as a purplish red
ruby or a purplish red sapphire
and borderline cases are not uncommon.
Sapphires
are noted for the large range of
colors in which they occur. The
name fancy sapphire, is used to
describe sapphires which are not
blue. Fancy sapphires are available
in an amazing range of colors including
yellow, green, violet, pink, brown,
purple, violet, white, black and
orange.
Occurrences:
The most notable deposits of Sapphire
are located in Burma, Australia,
East Africa, Sri Lanka, and Madagascar.
Other well known deposits include
Montana, USA; and Kashmir, India.
The deposit in Kashmir is no longer
producing and the deposits in Montana
may not produce enough to be commercially
viable.
The
Source: Many of the important
sapphire deposits in Sri Lanka,
Madagascar, Kenya and Tanzania are
geologically related to each other.
Australia, Antarctica, Sri Lanka,
Madagascar and Africa were all connected
in a super continent known as Pangaea
billions of years ago. Giant rivers
carried gemstones from the same
source and deposited them throughout
this super continent as alluvial
gravels. Between 200 to 400 million
years ago, the continents began
to separate as a result of tectonic
forces and continental drift.
The
same stones from the original deposit
are now found in Sri Lanka, Madagascar,
and Tanzania. Sri Lanka was probably
closest to the source and we know
this because the stones there are
larger with better crystallization.
As the stones were carried to what
is now Madagascar and Tanzania,
they would have became smaller and
more rounded because of the longer
distance they traveled. The largest
stones are in Sri Lanka.
Sri
Lanka: is well known for the
fine quality and broad range of
colors of the sapphires which are
found there. Almost every color
is found. Ratanapura is an important
center for mining and new stones
are offered on the local market
every day. Sri Lanka is known for
producing the largest and finest
sapphires in the world.
Treatments
The
traditional heating of rubies and
sapphires is a widely used and accepted
enhancement process which can improve
the transparency and/or the color
of the stones. The treatment is
permanent and heated stones do not
require special care.
New
treatments which are used to produce
orange and yellow stones are more
controversial The color is achieved
through a process which includes
the addition of foreign elements
to achieve the desired color alteration.
The treatment is a heat/diffusion
process which may or may not completely
penetrate the stone.
Because sapphires represent divine
favor, they were the gemstone of
choice for kings and high priests.
The British Crown Jewels are full
of large blue sapphires, the symbol
of pure and wise rulers. Since sapphire
symbolizes sincerity and faithfulness,
it is an excellent choice for an
engagement ring. When Prince Charles
chose a sapphire engagement ring
for Princess Diana, couples all
over the world were inspired to
revive this venerable tradition.
