Cochise College           Student Papers in Geology

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Roger Weller, geology instructor

by Melissa Cepero
Physical Geology
Fall 2011

Has Your Best Friend Been Lying to You?


      You know that famous song “Diamonds Are a Girl’s Best Friend” by Marilyn Monroe? The statement is obvious. Diamonds are considered a girl’s best friend. Though, the rock that you think of as your best friend, might be impersonating the real thing. Not many people realize that some jewelers swap out a real diamond with a cubic zirconia, although I’m sure that could be considering false sales or even illegal. Or what if your boyfriend asks you the big question and you’ve gone this whole time thinking the rock is a real diamond? Wouldn’t you like to know if what you have is the real thing? Well later on in the paper are some tests you can do to find out if you have the real thing, but until then you can do a little reading on the history and how these “fraternal twins” are made.


History of the Diamond


     We will most likely never know for sure when the first diamond was discovered but chances are diamonds could be a billion years old. Though according to Costellos, it’s been said that the first diamonds were discovered in India roughly around 800 BC. In this time the diamonds were most likely used as decoration or as protection from evil forces.


     Later in time, diamonds started to get used for medical purposes. One way that it was said that diamonds could be used medically was to hold a diamond in one hand while making the sign of a cross with the other hand. It was also said that if a person swallowed diamonds, the diamond would cure a person’s medical problems from the inside.


     Around the time of the middle ages that’s when diamonds started to earn their value. After everyone learned that diamonds weren’t just for decoration anymore, or even for medical uses, but worth money, people started telling stories to the mine workers who were searching for the diamonds. Miners were told that the diamonds were poisonous. This story went around so that the miners became scared of the diamonds and wouldn’t steal them by swallowing them. (1)



How Diamonds are Formed

According to, diamonds can be found about 90 miles below the surface of the Earth’s mantle where temperatures get up to 2000°F. Diamonds need exceedingly high temperatures and tremendous pressures in order to form, and under the Earth’s mantle is the perfect location. Question is how do diamonds 90 miles below the Earth’s mantle get to the surface? Diamonds get brought up to the surface from deep volcanic eruptions. Here are three processes of how diamonds can be formed that I found from

The Earth’s Mantle

Subduction Zones

Asteroid Impacts

Diamonds are kept trapped underneath the surface of the Earth’s mantle just until there is a volcanic eruption. This is how the diamonds get to the Earth’s surface. Also, diamonds need carbon to form. The carbon is believed to be trapped in the Earth from when it was formed.

Small diamonds have been found in rocks that are believed to have been pulled into the Earth’s mantle by tectonic plates. Then the diamonds get returned back to the surface from deep volcanic eruptions.

When an asteroid hits our planet, the asteroids cause impacts on the Earth’s crust creating high temperatures and a high amount of pressure. This is what a diamond needs to form, heat and pressure. There has been proof that small diamonds have been found surrounding the area of an asteroid impact.

Description: diamonds formed from deep source eruptions

Description: diamonds formed in subduction zones

Description: diamonds formed at asteroid impact sites





History of Cubic Zirconia

     Considering that jewelry with genuine stones cost so much money, some are unable to buy the “real thing”. Now-a-days you can buy a ring with cubic zirconia in place of a real diamond for a cheap amount to fool others to think what you have is a real stone.

     According to Man Made Diamond Info, cubic zirconia’s first came to be around in 1937 but it wasn’t until the 1970’s that the cubic zirconia’s became somewhat popular. It was first on the market in 1977, but the cubic ziroconia was still not as popular. It wasn’t until the 1980’s that CZ’s were produced big time. (4)

     Although, Geology Rocks states that when the Russians were making lasers, they had to use real rubies. Eventually the cost was becoming too much to keep up with. Russians had to import the rubies, and buying plus importing real stones became too expensive. So they came up with a simple solution. Create a stone with a similar structure, and is able to be cheaply made. Man Made Diamond Info says that the Russians started to use the cubic zirconia’s in 1973, then commercial production began in 1976. In time people decided that cubic zirconia’s were not only good for lasers, but also resembled diamonds. Later in time, the cubic zirconia’s started making their way into jewelry around the 1980’s. (2)

How Cubic Zirconia’s are Made

     Cubic Zirconia’s are mainly made up of zirconium oxide which means that the mineral is not found in natural form. When it was first made in the 1970’s, it was actually made in a microwave. The cubic zirconia needs heat just like a natural diamond needs to form. This temperature is at 2500°C and the teqnique that is used for making cubic zirconia’s is a process called the “Skull Melt”. In this process the material heats up from the inside and out. The outside of the casing stays at a cool temperature but in the mean time inside it is extremely. After the heat gets turned off then the product cools under controlled conditions the material hardens. The material that gets hardened is the cubic zirconia’s. (4) 


How Do You Know?

     There is no 100% way that you will be able to tell if the stone in your jewelry is real or not, unless you take a chance to damage it. Or you could take it to a jeweler who has knowledge on real or fake diamonds. Though, now some jewelers have a hard time distinguishing if the rock is real because of how far people have gone to make the ziconia’s look like the real thing. Here are 5 tests that you can do to get an idea of whether or not your best friend is the real thing.

Transparency Test:       This works best with an actual lose diamond because if it is embedded in jewelry the results won’t be so clear depending on the size of the rock. You have to flip the stone over and put it over newspaper. If you can see without a problem, and can read through the stone clearly, the stone is fake.


Fog Test:          This can work with either a lose rock or one that is in jewelry. Depending on the rock size, it will affect your ability to see the results. Also, if there is any dirt or oil on the stone that will also affect the results. So make sure the stone gets cleaned under warm water before doing the test. Fog the stone in your mouth. If the stone fogs for 2-4 seconds it is a fake. A real diamond will lose its fog almost instantly.


Fluorescent Test:         Many real diamonds glow under a black light, while 99% of fake diamonds do not glow. This could be an unreliable, yet a disappointing test because if the stone doesn’t glow it doesn’t mean that it’s a fake. It could just be a better quality diamond. Although, diamonds that do glow under a black light, don’t get excited because the diamond will lose 20% of its value.


Observation Test:         This test is probably best done under a microscope or a magnifying glass because it will be hard to see with the naked eye. If you look closely at the stone, you need to look at the edges or the corners. If the corners are sharp then the stone is probably real. If the edges are rounded it is most likely fake. You can also look for markings on the jewelry such as: 10K, 18K, 14K. Any of these would most likely have a real diamond. If it says CZ, it is not real.


Weight:            This test works best with a loose stone because the weight of the gold, silver etc. will affect the results of the test. Cubic Zirconias weight 55% more than a real diamond. (5)


1-      History of Diamonds. Web. 1 November 2011.

2-      Hill, John and Davis, Katie. Geology Rocks. 7 February 2007. Web. 1 November 2011.

3-      Geology. 2005-2011. Web. 1 November 2011.

4-      Man Made Diamond Info. 8 April 2010. Web. 1 November 2011.

5-      Diamond Cutters International. 11 December 2008. Web. 1 November 2011.

6-      Pearls-Necklace. 28 April 2011. Web. 21 November 2011.