Mercury

by

Joshua Converse

http://www.emporia.edu/earthsci/amber/go336/converse

This webpage project was created for a mineralogy course in November 2006 at Emporia State University. The assignment was to learn webpage creation, as well as present a summary of my knowledge regarding mercury.

Mercury is a mineral that interests me because it is liquid at room temperature. Also, mercury has been used in many different applications in the past, but not today. This webpage will inform you on why this has happened. It includes mercury background, origins, and properties, as well as environmental and health concerns.

Table of Contents

Background

Mercury has been known since ancient times and while the name mercury is Arabic in origin (Mineralogy Database, http://www.webmineral.com/data/Mercury.shtml), some think it is likely named for the planet nearest the Sun, which was named after the Roman god of travel (Mineral Information Institute, http://www.mii.org/Minerals/photomercury.html). Did the ancients think the mineral mercury and planet Mercury looked alike? This is unclear because mercury is a silvery metal, yet when combined with sulfur as in cinnabar, it is red. Also, mercury acquired the nickname of quicksilver or hydrargyrum, which is derived from Greek words, hydros, or water, and argyros, or silver (Mineral Information Institute). Silvery water was a more descriptive name and "the symbol for mercury, Hg, was derived from the name, hydrargyrum" (Mineral Information Institute).

Mercury is geographically dispersed. "Major world producers of mercury are Algeria, Kyrgyzstan, Spain, and China" (Mineral Information Institute, http://www.mii.org/Minerals/photomercury.html). Mercury was mined in the United States, mainly in the states of California, Arkansas, Oregon, Nevada, Idaho, and Texas (Mineral Information Institute). However, mercury deposits are no longer mined in those states and the U.S. imports mercury.

Citation


Images from http://www.mii.org/Minerals/photomercury.html (left) and (right)

Mercury is the only metal that is liquid at room temperature and because of the high density and surface tension, it forms the liquid spheres in pores of rock (Ameythst Galleries, mineral.galleries.com/minerals/elements/mercury/mercury.htm). It has a specific gravity over 13 and because it is liquid, there is no hardness, crystal structure, fracture, cleavage, or streak. When frozen it "forms crystals in the rhombohedral system at low pressure, and in the tetragonal system at high pressure (Ameythst Galleries).

Its native state is more commonly occuring in one of two minerals, cinnabar, a mercury sulfide or HgS, and calomel, a mercury chloride, HgCl (The Mineral and Gemstone Kingdom, http://www.minerals.net/mineral/elements/mercury/mercury.htm). Cinnabar is up to 86% mercury (Mineralogy Database, http://www.webmineral.com/data/Cinnabar.shtml). Mercury occurs in association with other mercury containing minerals, such as corderoite and livingstonite. Other minerals found in association with cinnabar are quartz, dolomite, pyrite, and calcite, among others (Mineralogy Database, Cinnabar-citation?).

The production of mercury is relatively easy compared to other minerals that come from an ore.
"The ore (cinnabar) is crushed to typically 1" to 2" in size then sent to a kiln. Simply heating the ore in a kiln to 1,100 degrees Fahrenheit, all of the mercury will vaporize into the kiln (mercury vaporizes at 675 deg. F). The kiln vapors then must be condensed, by cooling, to recover the mercury, which becomes liquid at temperatures below 675 deg. F and freezes solid at 2.5 deg. F" (citation?).

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Environmental Concerns

As you may know, mercury is now considered a toxic substance. In fact, the United States doesn't mine mercury for this reason. All mercury used in the United States is either secondary mercury, meaning that it has been used before or it is imported into the country. Even though mercury has recently been frowned upon in our society, its toxic nature was suggested in 1473 by Ulrich Ellenbog, who wrote a book on how mercury can trouble people but it was not printed until 1543 (Goldwater 261). In a 1932 translation of Ellenbog's book, he stated that, "This vapour of quicksilver, silver and lead is a cold poison, for it maketh heaviness and tightness of the chest, burdeneth the limbs and oftimes lameth them as often one seeth in foundries where men do work with large masses and the vital inward members become burdened thereform" (Goldwater 261). Since Ellenbog was just talking about the vapor of metal in general most people felt that he was not talking specifically about quicksilver (Goldwater 261). I find it amazing that this man figured out the effects of mercury over 500 years ago, yet it has only recently been regulated in the U.S.

In more modern English, here are the problems that arise from contact with mercury. "Mercury is a neurotoxin, which means it affects the nervous system. Once mercury is in the body, it causes nervousness, trembling, personality changes, and in extreme cases, even dimentia" (Mineral Information Institute). This article goes on to say, "Fish that ingest mercury compounds that may occur in streams and lakes can become a source of mercury poisining in humans" (Mineral Information Institute). After reading this, you can see why it is regulated, but why has it taken so long to be recognized since Ellenbog revealed this hazard many years ago?

Before I answer that question, it is instructive to think about where mercury is located and what applications mercury has had in the past. Mercury is found in throughout the environment such as rocks, soil, water, coal, petroleum, and air. The amount of mercury in rocks and soil is low, just trace amounts, but greater quantities are airborne. Mercury gets into the air by evaporation or natural weathering and erosion. Also, mercury can be airborne through volcanic explosions or as a consequence of burning fossil fuels such as coal or petroleum (Gray).

Although mercury occurs in trace amounts in coal, it is hazardous because of the enormous amount of coal that is burned for electrical uses everyday. "Thus, burning coal is the largest human-caused contributor of mercury to the atmosphere" (Gray). After mercury is airborne, it eventually comes back down to Earth with rain. This can contaminate soils, lakes, rivers, and oceans. If it does concentrate in oceans and lakes, evaporation will return it to the atmosphere again (Gray). Now it becomes obvious why mercury has to be regulated.

Now that we know that mercury can cause serious harm to humans and the environment, the demand for mercury has seriously declined. Not only this, but new technologies and environmental laws have helped to decrease the demand. For example, new laws call for lower mercury emissions from smokestacks and the careful disposal procedures (Mineral Information Institute). Even with these new laws, mercury still has some use in the manufacture of chlorine and caustic soda, and in many electrical applications. In the past, mercury was the main ingredient in batteries and in themometers. Mercury was alloyed with other metals and used for filling cavities in teeth left by decay (Mineral Information Institute).

Getting back to the earlier question about why it took so long to regulate mercury... I speculate that we ignored the hazards associated with mercury because it was thought to be such a useful product. Its many uses led to not taking the extra precaution to stop the production of mercury. Regulations in the U.S. seem to coincide with discovering good substitutions for mercury in the products that required mercury in the past.

Now however, as technology advances, people have created substitute or alternative sources for mercury. Batteries now contain zinc-air, lithium and nickel-cadmium. Ceramics are now used in filling teeth, and many electronic digital instruments have been used more to replace thermometers (Mercury 2).

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Conclusions

Mercury is a useful mineral substance, but one must weigh use with risk. While it is useful, mercury is a neurotoxin that is dangerous to humans and environment. Therefore, mercury is regulated and feared. After reading this webpage, I hope you have a greater appreciation of mercury and at the same time, realize the considerations that went into banning this liquid mineral product.

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Sources

For comments and questions, email jconvers@emporia.edu.

Related Links
California Geologic Survey,
www.consrv.ca.gov/cgs/
minerals/hazardous_minerals/mercury/ 		Mercury and Terlingua,
www.utexas.edu/tmm/exhibits/
glen_evans/geology/mercury_and_terlingua.html

Return to the mineralogy student webpages, www.emporia.edu/earthsci/amber/go336/webpages.htm.

Page created November 30, 2006. Copyright 2006 Joshua Converse.