Cyanide Leaching vs Precious Metals

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What is Cyanide?

Cyanide is a rapidly acting, potentially deadly chemical.

“Cyanide” can mean any one of various compounds containing the chemical group CN: one atom of carbon (C) and one atom of nitrogen (N). Because it is organic, it reacts readily with living organisms.

Cyanide easily combines with many metals – making it useful in separating metals like gold from their ore.

A sodium cyanide solution is commonly used to leach gold from ore. There are two types of leaching:

· Heap leaching: In the open, cyanide solution is sprayed over huge heaps of crushed ore spread atop giant collection pads. The cyanide dissolves the gold from the ore into the solution as it trickles through the heap. The pad collects the now metal-impregnated solution which is stripped of gold and resprayed on the heap until the ore is depleted.

· Vat (or tank) leaching: The ore is mixed with cyanide solution in large tanks. Although the chances of spills are lower because the leaching process is more controlled, the resulting waste, known as tailings, is stored behind large dams (tailings impoundments) which can and do fail catastrophically.

· Leaching is attractive due to the low capital cost involved but is a slow process and the extraction efficiency is a relatively low 50-75%.[2]

Because cyanide leaching is very efficient (compared to other currently used processes), it allows profitable mining of much lower ore grades.

Mining lower grade ore requires the extraction and processing of much more ore to get the same amount of gold. Partially due to cyanide, modern mines are:

· much larger than before cyanide was used;

· create vast open pits; and

· produce huge quantities of waste. 

More than 20 tons of mine waste are generated to produce enough gold for a typical ring.

Cyanide is highly toxic, and can result in substantial environmental impacts and public health risks if released into the environment. Cyanide spills have resulted in major fish kills, contaminated drinking water supplies and harmed agricultural lands. For example:

· Mexico, 2014: 500,000 gallons of cyanide solution spilled from a retaining pond at the Proyecto Magistral mine, after heavy rains.

· Kyrgyzstan, Kumtor Gold Mine, 1998: A truck carrying 2 tons of sodium cyanide crashed into the Barskoon river, resulting in more than 2,000 people seeking medical care.

· Romania, Aural Gold, 2000: A tailings dam ruptured, spilling 3.5 million cubic feet of cyanide-contaminated waste into the Tisza and Danube Rivers, killing fish and poisoning water supplies as far as 250 miles downriver in Hungary and Yugoslavia.

· United States, Zortman-Landusky Mine, Montana, 1982: 52,000 gallons of cyanide solution poisoned the aquifer that supplies fresh drinking water for the town of Zortman. The accident was discovered when an employee of the mine noticed the smell of cyanide in his tap water at home.

Industry claims cyanide is relatively safe because — even if it spills — it breaks down rapidly in surface water.

But the compounds that cyanide breaks down into can be harmful.

Cyanide spills into groundwater can persist for long periods of time and contaminate drinking water aquifers.  Cyanide contaminated groundwater can also pollute hydrologically connected neighboring streams.

For example, at the Beal Mountain Mine in Montana which closed in 1998, cyanide seeped into groundwater that feeds neighboring trout streams, resulting in cyanide violations in those streams long-after the mine closed.

[1] https://earthworks.org/issues/cyanide/ 

[2] https://www.cyanidecode.org/cyanide-facts/use-mining

Industry Description, Major Products and Services

Companies in the gold and silver mining industry develop mine sites, mine and quarry gold and silver, and prepare gold and silver for sale. Many gold and silver mining companies also mine for other metals. Mining of iron, nickel, copper, and other metals, including gold and silver, is covered in the Metal Ore Mining Industry.

Major Companies Within The Industry

Major companies include Canada-based Barrick Gold, Kinross Gold, and Goldcorp as well as Newmont Mining (headquartered in the US), AngloGold Ashanti (South Africa), KGHM (Poland), Fresnillo (UK-based with primary operations in Mexico), Glencore (Switzerland), and Polymetal International (UK).

Industry Size

Worldwide, the industry produces about 3,200 metric tons of gold and 27,000 metric tons of silver annually, according to Thomson Reuters. Of those totals, the US accounts for about 230 metric tons of gold and 1,000 metric tons of silver. Gold ore is primarily mined in China, Australia, Russia, the US, and Canada. Mexico, Peru, China, Chile, and Russia are the top silver production locations.

The US gold and silver mining industry includes about 190 establishments (single-location companies and units of multi-location companies) with combined annual revenue of about $13 billion.

Demand and Profitability

Demand is driven by industrial production and economic growth. Individual company profitability depends on volume and operating efficiency.

Advantages and Profitability Related to Size of Firm

Large companies have more resources to devote to discovering and developing new deposits. Small companies typically own just one mine and limit exploration to that one property. 

[1] http://www.firstresearch.com/industry-research/Gold-and-Silver-Mining.html

Industry Description, Major Products and Services

Companies in the Metal Ore Mining industry develop mine sites, mine and quarry metallic minerals and provide related support services and prepare minerals for sale. The industry includes companies that mine and process gold, silver, copper, nickel, lead, zinc, iron ore, uranium, and other metals.

Major Companies Within The Industry

Major companies include Freeport-McMoRan and Newmont Mining (both based in the US), as well as Anglo American (UK), China Molybdenum, BHP Billiton and Rio Tinto (both dually headquartered in Australia and the UK), Glencore (Switzerland), Grupo Mexico, MMC Norilisk Nickel (Russia), and Vale (Brazil).

Industry Size

China, Australia, Chile, and South Africa dominate the global metal ore mining industry. The world's most highly mined metals are iron ore, bauxite, aluminum, chromium, copper, manganese, zinc, and silicon. Fueled by eco-nomic growth and higher spending among construction and manufacturing industries, mining companies in China are expected to experience strong growth over the next several years.

The US metal ore mining industry includes about 330 establishments (single-location companies and units of multi-location companies) with combined annual revenue of about $22 billion, as well as about 225 establishments (single-location companies and units of multi-location companies) that provide related support services and generate annual revenue of about $1.6 billion.

Demand and Profitability

Demand is driven by industrial production and economic growth, both domestic and foreign. Individual company profitability depends on volume and operating efficiency.

Advantages and Profitability Related to Size of Firm

Large companies can afford to discover and develop new deposits and increase reserves.

[1] http://www.firstresearch.com/industry-research/Metal-Ore-Mining.html