Adopt-a-Mineral Project: Malachite and Beryl
Stephanie Trump

A mineral is defined by the textbook as a naturally occurring chemical compound with a regular crystal structure (Wenk and Bulakh, 2004). A crystal is a homogeneous compound with the atoms arranged in a regular periodic pattern (Wenk and Bulakh, 2004). The arrangement of the atoms into crystals had been speculated about for a while, but was only shown to be true in 1912 when Max von Laue irradiated crystals with X-rays and observed the diffraction (Wenk and Bulakh, 2004).

The term mineral comes from the Latin mina, meaning mine, and crystal comes from the Greek word, crystallos, meaning ice. This name was used for quartz, which the Greeks thought was water that had become ice at very high pressure deep inside the earth. The study of minerals and crystals is called mineralogy, which is a very old branch of science. Ancient Greeks and Romans wrote books on the subject. The first known book on minerals was written about 300 BC by the Greek philosopher Theophrastus (Wenk and Bulakh, 2004). Mineralogy is a subfield of the geosciences that includes crystallography and mineral genesis, and well as the physical, chemical, and optical properties of naturally occurring, crystalline solids (S. Aber, pers. comm. 8/2007).

To learn more about two specific minerals, malachite and beryl, read on...

Malachite

The image to the right is malachite and a copper penny for scale. The photo was taken by the author, Stephanie Trump (9/2007).

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Beryl

Beryl is a mineral composed of beryllium, aluminum, oxygen, and silcon. The chemical formula is Be₃Al₂Si₆O₁₈. It can be green, colorless, white, blue, greenish blue, golden yellow, brown-yellow, red, and pink. Green beryl is called emerald, blue-green is aquamarine, colorless is goshenite, yellow is golden beryl, yellow-brown beryl is called heliadore, and the pink beryl is called morganite. It has a vitreous luster and colorless steak. Beryl has a hardness of 7 1/2 to 8 and an uneven to concoidal fracture. Beryl most often occurs in hexagonal crystals, but can, rarely, form tabular crystals. When tabular crystals are present, they will most often be found in morganite.

Beryl is found in metamorphic pegmatites. The different colors are caused by various chemical substitutions. Green color is caused by cromium or vanadium at the aluminum sites, though it can only be called emerald if it contains chromium, not vandium. If the green color is caused by vandium, it is just green beryl. The blue-green color of aquamarine is caused by iron substituting for the aluminum. Magnesium is what causes morganite to be pink, and iron substituting for the silcon causes the yellow-brown color of heliodor.

Beryl is a ring silicate. Some high-quality beryls are valued as gemstones. Beryl is often used as a source of beryllium and as a gemstone.

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References

• Barthelemy, David. (2005). Mineralogy database. 24 August 2007. WWW URL www.webmineral.com.
• Busch, R., Dyar, D., and Wiswall, G. (1998). A study of minerals. CD: Tasa Graphic Arts, Inc., 1.5. Albuquerque, N
• Chesterman, Charles W. (2005). National Audubon society field guide to North American rocks and minerals. Alfred A. Knof, Inc, New York.
• Pough, Frederick H. (1996). Peterson field guides: Rocks and minerals. Houghton Mifflin Company, New York.
• Scovil, Jeffery. Geopolis. October 26, 2007. www.geopolis-fr.com/mineraux-beryl-3.html.
• Wenk, H.R. and Bulakh, A.(2004). Minerals: Their constitution and origin. Cambridge University Press, United Kingdom.

For more information email strump@emporia.edu. Webpage created September 2007; latest update 12-1-2007.