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Roger Weller, geology instructor

wellerr@cochise.edu

Graphite
by Fernando Gomez
Physical Geology
Fall 2015
  
 
                                            
    Graphite
 

http://vignette3.wikia.nocookie.net/powerlisting/images/c/cc/Graphite.jpg/revision/latest?cb=20130331015258

Photo courtesy of Roger Weller

http://skywalker.cochise.edu/wellerr/mineral/graphite/graphiteL.htm

 

 

Discovery of Graphite

 

            Graphite was discover before the early 1500’s, where there was a large amount of graphite at Seathwaite Fell near to Borrowdale in Cumbria, England. The people who lived in there used this mineral for marking sheeps. They found that it was a very useful tool for marking them, since graphite it’s a black mineral.
 

https://jillsbooks.files.wordpress.com/2015/03/p1260215b.jpg?w=500&h=375

 

Where does the word “Graphite” comes from?

          
  The word “graphite” comes from the Greek word (graphein) which means “to write or to draw.” This name was given by the German chemist  and mineralogist Abraham Gottlob Werner, in the year 1789.
 

The formation of graphite is considered to most often found as flakes or crystalline layers in metamorphic rocks such as marble, schist’s and gneisses. Graphite may also be found in organic-rich shale’s and coal beds. In these cases, the graphite itself probably resulted from metamorphosis of dead plant and animal matter. Graphite is also found in veins and sometimes in basalt. Graphite also occurs in meteorites.

 

Example of graphite formation:

 

 http://www.nature.com/ngeo/journal/v6/n6/images/ngeo1827-f3.jpg

 

Properties of Graphite
 

Graphite has many distinctive properties which makes it a very interesting mineral. Graphite is a soft, slippery, grayish-black substance. It has a metallic luster and is opaque to light. It is a good conductor of heat and electricity. Although graphite is a very stable allotrope of carbon but at a very high temperature it can be transformed into artificial diamond. Chemically, graphite is slightly more reactive than diamond.

 

Types and Varieties of Graphite
 

          We have different types of graphite and they are considered by its quality and its formation.  The first type of graphite I am going to present, it’s called “Lump Graphite.” Lump graphite is considered the most valuable, and the highest quality form of natural graphite. It is formed by the direct deposition of solid, graphitic carbon from subterranean, high temperature fluids. Since Lump Graphite has the highest quality, it has a distinct competitive applications.

 

sri_lanka_lump_art.jpg
 

 

The second and less expensive type of graphite is the Crystalline Flake or the (Flake Graphite).  It occurs as isolated plate-like particles with hexagonal edges if unbroken and when broken the edges can be irregular or angular. It has a distinctive plate-like or ‘flake’ formation. Flake graphite is subdivided into large, medium and fine sizes and is a less common form of natural graphite.
 

 Graphite is formed in metamorphic rocks or calcareous sedimentary rocks. The grade of flake graphite ranges from 10-12% Cg, and the purity varies from 85-95% carbon after refining. Natural flake has the widest range of use and accounts for about 49% of natural graphite consumption.

 https://graphene-supermarket.com/images/XC/HC%20Graphite/Flake-Graphite-1-SEM.jpg
 

The third type of graphite is the Amorphous Graphite
 

      Amorphous graphite is the most abundant form, but occurs at the lowest in grades than other natural graphite and is the most abundant. It is formed by the metamorphism of previously existing anthracite coal seams. The term “amorphous” refers to its very small crystal size of particles, which are not visible unless viewed under magnification. Large amorphous graphite deposits are found in China, Mexico, and the United States.
 

 

 http://www.tritonmineralsltd.com.au/wp-content/uploads/2015/04/amorphous-02.jpg

 

 

 

Synthetic Graphite
 

The Synthetic graphite is made by heating high carbon materials, like petroleum coke and coal tar pitch to temperatures in the range of 2500 to 3000 degrees Celsius. At these high temperatures, all volatile materials and many metals in the feedstock are destroyed or driven off. The graphite that remains links into a sheet-like crystalline structure. Synthetic graphite can have a purity of over 99% carbon, and is used in manufactured products where an extremely pure material is required. 
 

 

 http://www.trade2cn.com/upload/20111017/065308/HBWH12045-1.jpg
 

Uses of Graphite
 

          The major use of graphite is in making lead pencils of different hardness, by mixing it with different proportions of clay. The weakly held layers of carbon atoms in graphite easily slide over each other and are left behind on paper as black marks.

 

Graphite is used as a dry lubricant in machine parts. Since graphite is a mineral made of loosely bonded sheets of carbon atoms. Also, it is slippery texture that makes it a very effective lubricant.  Being resistant to chemicals and having a high melting point and also because it is a good conductor of heat, graphite is used to make crucibles.  The presence of free electrons makes graphite a good conductor of electricity and it is used to make electrodes.  Graphite has the ability to absorb fast-moving neutrons, thus, it is used in nuclear reactors to control the speed of the nuclear fission reaction.
 

Sources
 
http://powerlisting.wikia.com/wiki/Graphite_Manipulation
https://uwaterloo.ca/earth-sciences-museum/resources/detailed-rocks-and-minerals-articles/graphite
http://www.newworldencyclopedia.org/entry/Graphite

http://www.saintjeancarbon.com/index.php/graphite/about-graphite/
http://geology.com/minerals/graphite.shtml

 

 

Images

 

https://graphene-supermarket.com/Flake-Graphite-100-grams.html

http://www.nature.com/ngeo/journal/v6/n6/ http://geology.com/minerals/graphite.shtml full/ngeo1827.html

http://www.trade2cn.com/upload/20111017/065308//HBWH12045-1.jpg