Gemstones

Kearstyn Ritter

Education 373

Spring 2010

My ExperienceTwo summers ago I began working at

Tracy Zeller Jewelry. I began working with jewelry items such as gold, sterling silver, gemstones, & diamonds. I also learned about the quality of stones and what is considered a “good diamond/gemstone”. I learn more and more about these every day. However, I still have more questions.

My Questions

1.Where to find gemstones?

2.How are gemstones formed?

3.How are synthetic gemstones made?

4.What are the types? How many types?

Standards

• 4.3.6 Recognize and describe that rock is composed of different combinations of minerals.

• 6.3.14 Give examples of some minerals that are very rare and some that exist in great quantities.

• 7.3.9 Explain that sedimentary rock, when buried deep enough, may be reformed by pressure and heat, perhaps melting and recrystallizing into different kinds of rock.

Where to Find Gemstones?• Mined in Earth’s crust• The crust is made up of three kinds of rocks, known

in geology as igneous, metamorphic and sedimentary • Some gemstones are associated especially with one

kind of rock; others with multiple types.

http://www.gemselect.com/other-info/gemstone-formation.php

Where certain stones are mined in all the parts of the world! Very interesting to know what stones the USA mines for! I thought all of our stones came from overseas.

Formation of Gemstones• Igneous minerals are created with heat. They are minerals that are created deep within the earth. Metamorphic refers to conditions where heat and pressure change existing minerals into something new. Sedimentary rocks are based on deposits of sediment.

http://www.gemsociety.org/info/igem17.htm

Formation of Gemstones

• There are different ways stones can form.– Molten Rock & Associated Fluids – Environmental Changes – Surface Water – Gems Formed in the Earth's Mantle

Molten Rock & Associated Fluids• As the main magma body cools, water originally present in low

concentrations becomes concentrated in the molten rock because it does not get incorporated into most minerals that crystallize. Consequently, the last, uncrystallized fraction is water rich.

• The high water content of the magma makes it possible for the pegmatite crystals to grow quickly

• Gems crystallize from solution when it encounters open spaces such as cracks. As a result, 'veins' of minerals fill preexisting cracks.

• When the pegmatite magma is rich in beryllium, crystals of beryl form.

• If magmas are rich in boron, tourmaline will crystallize

http://nature.berkeley.edu/classes/eps2//wisc/Lect3.html

Environmental Changes

• The temperature and pressure can rise to the point where existing minerals are no longer stable.

• Under these conditions, minerals can change into different species without melting.

• This is known as metamorphism • Types of gemstones formed from this are: garnets,

corundum, lapis or marcasite.

http://www.gemsociety.org/info/igem17.htm

Surface Water• Water near the Earth's surface

interacts with minerals and dissolves them

• The mineral that forms is determined by what the dissolved elements are.

• If the water has interacted with silica-rich rocks silica-rich minerals will form: amethyst (quartz); agate; and the formation of opal.

• If the water has interacted with copper-rich rocks, copper minerals will form: malachite and azurite; or turquoise.

http://nature.berkeley.edu/classes/eps2//wisc/Lect3.html

Gems Formed in the Earth's Mantle• The most notable examples of gems formed in the earth's

mantle are diamond and peridot• Diamonds are made from carbon. The stable form of carbon

at the Earth's surface is graphite. High pressures and temperatures are required to convert graphite to diamond. Thus, almost all diamonds formed about 100 miles below the Earth's surface. Dates suggest that their formation was restricted to in the first few billion years of Earth history.

http://www.gemsociety.org/info/igem17.htm

How Synthetic Stones are Made• These types of stones are grown in a laboratory.• These stones essentially have the same appearance,

physical, and chemical properties as the natural. • These are a less expensive version of the real stone.• Imitation stones are made of glass or plastic.

(This is what I thought synthetic stones were. I would’ve never thought that they were made of the same properties as the natural.)

Types of Gemstones• Diamonds• Tourmaline-• Corundum

– Sapphires & Rubies• Chrysoberyl

– Alexandrite• Quartz

– Onyx, Amethysts, & Citrines

• Beryl– Emeralds & Aquamarines

• Feldspar • Organic– Pearls & Amber

(Never knew that there were these categories. I thought every stone was its own type)

How many Gemstones

• There are more than 100 types of gemstones• I could not find a specific count• This is something I will have to try to explore

more. • Why is there no listed number?

ResourcesWebsitesCollege of Natural Resources - UC Berkeley. Web. 26 Apr. 2010.

<http://nature.berkeley.edu/classes/eps2//wisc/Lect3.html>."Gem Formation." International Gem Society. Web. 26 Apr. 2010.

<http://www.gemsociety.org/info/igem17.htm>."How Gemstones Are Formed." GemSelect - Buy Loose Gemstones from the

Source - Precious and Semi-Precious Gemstones. Web. 26 Apr. 2010. <http://www.gemselect.com/other-info/gemstone-formation.php>.

Books Bonewitz, Ra. Rock and Gem. New York: DK Pub., 2005. Print. Cook, David C., and Wendy L. Kirk. Minerals and Gemstones: 300 of the

Earth's Natural Treasures. San Diego, Calif.: Thunder Bay, 2007. Print.Holden, Martin. The Encyclopedia of Gemstones and Minerals. New York:

Facts on File, 1991. Print. Read, Peter G. Gemmology. Oxford: Butterworth-Heinemann, 1999. Print. Symes, R. F., and R. R. Harding. Crystal & Gem. New York: Knopf, 1991. Print.