Cochise College Student Papers in Geology
Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
Diamonds and Pearls
Erin E. Unger
Physical Geology
Spring 2009
Just Icing On The Cake
Tiffany & Co., or Blue Nile are the jeweler’s that flash through the mind
when a set of exquisite tear drop pearl earrings is seen gracefully dangling
from a ladies ear; or when a diamond engagement ring captures the eye with its
shining beauty. Both diamonds and pearls are made into beautiful pieces of
jewelry although how each gem is created, the set or mount in different pieces
of jewelry and the care of the gems once set, is as different as a diamond is
from a pearl.
The carbon that makes
diamonds comes from the melting of pre-existing rocks in the Earth's upper
mantle, or crust. There is an abundance of carbon atoms in the mantle.
Temperature changes in the upper mantle forces the carbon atoms to go deeper
where it melts and finally becomes new rock, when the temperature reduces. If
other conditions like pressure and chemistry is right then the carbon atoms in
the melting crustal rock bond to build diamond crystals, thus diamond deposits.
Of all the diamonds mined in the world each year, less than half are gem
quality. Gem quality diamonds are the diamonds used in jewelry. The clarity of
these diamonds ranges from flawless to inclusions and flaws visible to the naked
eye.
The harvesting of diamonds is done through pipe mining.
Pipe mining refers to the extraction of diamonds from volcanic pipes. In most
countries, a diamond pipe mine is composed of kimberlite, or blue ground. After
the diamond-bearing rock is brought to the surface, it is then transported to a
screening plant where the diamonds are separated from the host rock.
Diamond cutting and polishing requires several hours or
several months to complete. The rough diamond is divided into two parts by
sawing or cleaving. Most stones are sawn across the "grain" (visible evidence of
the diamond's crystal structure). Once the polishing of the diamond begins; one
by one, facets will be ground on to the stone. Most diamond cuts have 58 facets.
A well-cut diamond will be fiery, brilliant and beautiful. A well cut and
polished diamond will be one of these three cuts; the round cut, the princess
cut, or the emerald cut.
To clean diamond jewelry, it is best to use an ammonia
water mixture, and gently scrub the jewel’s surface with a tooth brush. Also
storing these pieces separately from other jewelry will protect it from being
scratched or chipped. Each glittering stone can be set in many different ways to
make many different items including; engagement rings, necklaces, pendants,
bracelets, earrings and watches.
Most of today’s pearls are cultured instead of being harvested naturally. Pearls are formed by an oyster’s reaction to an irritant getting inside of it. Over a long period of time an oyster will cover the irritant with many layers of a substance called nacre to protect itself. This process of layering the grain of sand with nacre results in a beautiful lustrous pearl. There are many different kinds of pearls each one being a different color, shape, or type. The color of a pearl can be white, white rose, black, silver, gold and pink. Pearls can be round, off-round, oval, teardrop, and semi- baroque. The types of pearls include; freshwater, akoya, south sea, and Tahitian. To harvest pearls workers have to pry open oysters, and separate the two shell valves, by cutting the adductor muscle, making an incision on the gonad and squeezing the pearl out. Machines used for pearl extraction go about this process by dissolving the oyster soft body parts with the use of chemicals while the pearls remain as they are and become easily extractable. Once the pearls are harvested they are washed in distilled water, polished with refined salt and sorted for sale according to size, color, shape, and luster. The care and maintenance of pearl jewelry is an easy task. Simply by wearing the jewelry, the natural oils in the skin keeps pearls lustrous, so the more often they are worn, the more beautiful they will look. Along with wearing them, they should be wiped off with a soft cloth after each time they are worn. Pearls can be set and mounted in any manner, just like diamonds can be. A quality string of pearls is recognized by a knot placed between each pearl on the string so that one pearl is not rubbing against the one next to it.
All diamond and pearl jewelry creations are of stunning elegance and
captivating originality, they are designs that bring glamour to life and will be
cherished always. Bracelets can range from grandeur, to simple elegance.
Necklaces and pendants are poetry in motion, captivating all as they proclaim
one’s personal style, and taste. So with this thought in mind, we can make the
determination that both diamonds and pearls are extraordinary works of art, from
the beginning formation of each, all the way through to the display cases in
jewelry stores around the world.
Works Cited
http://www.gemsutra.com/diamonds.html
http://www.costellos.com.au/diamonds/mining.html
http://www.fao.org/docrep/field/003/AB726E/AB726E13.htm
http://www.handwovenbands.com/index.htm
http://www.bluenile.com/diamonds/diamond-education?track=58
http://www.iamparadise.com/iamparadise/dept.asp?s_id=0&dept_id=158&gclid=CPPisbChqY8CFQgZhgode3gnJg
http://skywalker.cochise.edu/wellerr/aawellerweb.htm
Photo credits
http://skywalker.cochise.edu/wellerr/aawellerweb.htm
http://www.handwovenbands.com/index.htm