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Fast Facts:

Formula: Al2O3

System: Hexagonal

Hardness: 9

Color: Red

Occurence: Worldwide in igneous and metamorphic rocks, or as waterworn pebbles in alluvial deposits. Mainly in Myanmar, Thailand, and India.

Beautiful Ruby Jewelry

The shaded area is Myanmar

Ruby Miners Beside Massive Limestone Boulders

Corundum

Cut and Polished Ruby

A Mong Hsu Ruby in the Host Rock

Fun Ruby Quotes:

"The glowing Ruby should adorn
Those who in warm July are born,
Then will they be exempt and free
From love's doubt and anxiety."-Anonymous

"Who can find a virtuous woman? for her price is far above rubies."-The Bible

RUBIES

This web page tells you:

1. Fast Facts of Rubies

2. Why rubies are valued geologically and monetarily.

3. Where prominent rubies are found, and their legend.

4. Ruby composition.

5. How rubies form naturally versus how they are created in a laboratory.

Valuable Gems

Rubies are valued geologically for their immense hardness, high specific gravity, and crystal shape. They are valued monetarily for their beauty, attractive fiery red color, and as the July birthstone. They are also wonderful to use in jewelry-making because of the frequent twinning of the crystals, making liable fractures.

Prominent Ruby Deposits

The most prized ruby deposits are those of Central and South-East Asia. The Mogok deposit in Myanmar (ex-Burma) produces the highest quality rubies, reputed for their intense "pigeon blood" color and their transparency. "Pigeon Blood" is a term used for the finest hue of rubies.

Rubies are mined in Myanmar using five different methods: pit-method, open-trench, tunneling, open-cast, and 'lu'. A ruby larger than 10 carats is worth more than an equivalently sized diamond, because it is so rare.

More about the Mogok Deposit:
http://www.ruby-sapphire.com/pigeons-blood-mogok.htm

Fresly Mined Rubies

The Legend:

Long before the Buddha walked the earth, the northern part of Burma was said to be inhabited only by wild animals and birds of prey. One day the biggest and oldest eagle in creation flew over a valley. On a hillside shone an enormous morsel of fresh meat, bright red in color. The eagle attempted to pick it up, but its claws could not penetrate the blood-red substance. Try as he may, he could not grasp it. After many attempts, at last he understood. It was not a piece of meat, but a sacred and peerless stone, made from the fire and blood of the earth itself. The stone was the first ruby on earth and the valley was Mogok.

Composition and Formation

Rubies are made up of the mineral corundum. Corundum is aluminum oxide ( Al2O3). A ruby forms when there is a small impurity of chromic oxide in the corundum (an aluminium oxide in which some of the aluminum ions have been substituted by chromium). This substitution process is called an isomorphous replacement. Chromium and vanadium, another metal constituent of rubies, provide the fiery red color of the crystal. If the stone formed in the corundum is not red, it is a sapphire, although the name is commonly associated with only blue stones.

Example of Corundum

Another name for Corundum is Emery. On Mohs Scale of Hardness, Corundum is a 9, just under diamonds (10).

Ruby crystals form at high temperatures, between 620 and 670°C. They appear to be the features of distal hydrothermal reactions with marble. "They are formed mainly in high-grade metamorphic environments where hydrothermal fluids meet limestone," (Waltham, 1999, p. 144). When there are rutile inclusions present in cabochons, there is a star effect.

Star Effect

Rubies can also be created in a laboratory, using two different methods: Flame-Fusion and Flux-Growth.

The cheapest method of producing synthetic rubies is the flame-fusion process. The chemicals are melted and dripped onto a boule. The melt then crystallizes within a matter of hours. The result is an unnatural, glassy stone with curved growth plates. Instead of inclusions, flame-fusion rubies have tiny gas bubbles. They cost $1-4 per carat. Such a ruby is often used in costume jewelry.

Trillion Cut Ruby

The flux-growth method involves dissolving the chemicals into a molten mixture, called a flux. The gem is inserted into the flux, and it crystallizes under controlled-pressure conditions. It takes up to six months for the crystal to form. The growth planes are straight, making the crystal structure look more like a natural ruby. Often flux-growth rubies have inclusions which only skilled gemologists can decipher from natural ruby inclusions. Flux-growth rubies can range in cost from $100-500 per carat. Because these rubies look so real and are much more affordable, many people buy them... but no geologist ever would!

Literature Cited

*CLICK ON ANY IMAGE TO VIEW ITS SOURCE

Mershak, Stephan. Essentials of Geology. W.W. Norton & Company, Inc., 2004, New York.

Waltham, Tony. The ruby mines of mogok. Geology Today, 1999, 15(4) p. 143.

Hall, Cally. Gemstones. Dorling Kindersley, Inc., 1994, New York.

http://www.geotimes.org/current/NN_rubies.html

http://hyperphysics.phy-astr.gsu.edu/hbase/minerals/ruby.html

http://scienceblog.com/community/article2255.html

http://www.geocities.com/Eureka/Office/3962/synthetics.html

http://www.mindat.org/min-3473.html

http://www.eurekalert.org/pub_releases/2004-02/idrp-arc020304.php

http://www.ruby-sapphire.com/pigeons-blood-mogok.htm

Link to other Student Webpages for 2004 Earlham Physical Geology

Copyright © 2004 Earlham College. Revised April 19, 2004 . Send corrections or comments to parkero@earlham.edu