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Cotton Boll Conspiracy: Where Did All The Mercury From Mining Go?

Advances in US mining in recent decades have helped reduce the industry’s impact on the environment. While there is still room for additional progress, the difference between today and 125 years ago is staggering. Consider the amount of mercury that was used – and ultimately dumped – into western rivers in the second half of the 19th century in the quest for silver.

Mercury, or as it was better known then, quicksilver, was critical in the removal of silver and gold from ore in the western United States. As the Alta California newspaper noted in 1890, it was pretty easy to determine how much mercury ended up rivers, streams and land: however much was used.

“In the silver mines of a certain region, in order to ascertain the amount of quicksilver dissipated and lost, it is only necessary to know the amount bought, for not an ounce is ever sent out from the mines to be sold,” the publication wrote in January 1890.

The paper estimated that between 1860 and 1889, more than 20.5 million pounds of mercury was used just in the huge silver strikes in the Comstock Lode in western Nevada. While some was likely vaporized, making the surrounding atmosphere toxic, most of the element seeped into the environment, according to the Alta California.

In Nevada, mercury was used to extract silver and gold from ore through the Washoe Process, a concentrating process in which silver was mixed with mercury, either in a drum or on an amalgamation table, where the precious metal bond with mercury. The resulting product was called amalgam.

The silver was then recovered from the mercury by retorting, which involves distilling off the mercury from the amalgam.

Unlike today, 19th century miners evaporated off the mercury, but then allowed it to escape into the surrounding environment afterward.

“The great part of this lost quicksilver is no doubt strewn along the channel of the Carson River, though a vast deal lies in the soil in the vicinity of mining works,” the Alta California wrote. “When an old silver mill is torn down and removed its site is a rich mine in which to delved. The soil beneath where the mill stood is found to be impregnated to a depth of several feet with quicksilver and amalgam of the precious metals.”

Given the dangers of mercury, it’s surprising life in any form survived in the region following the promiscuous dumping and leaching that took place over more than 50 years.

Mercury isn’t something you want to mess around with, and it certainly isn’t something you want to haphazardly allow to filter into rivers, streams and the environment – not that miners 150 years ago were aware of the toxicity of the element.

Consider the warning listed on material safety data sheets for mercury, included with every shipment of the element:

Danger! Corrosive. Harmful if inhaled. May be absorbed through intact skin. Causes eye and skin irritation and possible burns. May cause severe respiratory tract irritation with possible burns. May cause severe digestive tract irritation with possible burns. May cause liver and kidney damage. May cause central nervous system effects. This substance has caused adverse reproductive and fetal effects in animals. Inhalation of fumes may cause metal-fume fever.

The bottom line: mercury is highly toxic and can cause serious illness and even death in both humans and animals.

In addition, mercury does not break down in the environment. It can build up in humans and animals and become highly concentrated in the food chain. That means animals, including humans, that eat other animals heavy in mercury content can suffer deleterious effects.

The Alta California estimated that between 1860-65, about 3.7 million pounds of mercury was used and wasted, meaning it was allowed to seep into the environment. Over the next 10 years, more than 7.3 million pounds ended up in streams, rivers and land. And between 1875 and 1889, the year prior to the publication of the article, another 9.5 million pounds of mercury disappeared into the environment.

No question, efforts at the Comstock Lode were bountiful. The discovery in 1857 represented the first major silver strike in the US, and Nevada is commonly called the “Silver State” because of the precious metal taken from the Comstock Lode.

In the many decades that the Comstock Lode was mined, more than $700 million worth of silver and gold, mostly the former, were taken out, precious metals worth many billions in today’s dollars.

Yet, the environmental impact continues to be felt. At present, the Comstock mines are contaminated with levels of mercury 26 times higher than the federal standard.

Considering that silver mining continued at the Comstock into the 20th century, and that mining took place in other parts of the West, including the California Sierras, there’s no doubt far more mercury found its way into the environment than the figure cited by the Alta California in 1890. No doubt a good bit is still there.



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