Gold and Diamonds: The Social and Environmental Impacts of Mining for the Diamond Ring

Phase 2: Extraction

The extraction phase of the life cycle assessment encompasses all aspects of mining and extraction of raw minerals and metals. While mining is a large part of the Canadian economy, it has extensive environmental impacts that need to be considered. The extraction of raw materials is one of the biggest concerns for environmental impacts in the life cycle assessment of a diamond ring.

Two main types of mining methods are the surface method, and the underground method. The former, is used when the deposit is located over a broad area close to the surface. The latter, is used when there is a high grade deposit over a smaller area deeper beneath the surface. Most of the world’s mines are open-pit mines, which are large craters blasted into mostly environmentally or historically protected areas.¹¹ Open-pit mines generate large amounts of waste rock which has made groundwater thousands of times more acidic than battery acid.

There are very large inputs involved in the mining process. Land resource use varies dependant on the method being used for extraction; surface mining covers a large land area and can cause extensive land disturbance due to removal of overburden (soil and surface rock) and vegetation. Water is used throughout this phase, most notably in separation and drilling. Surface and groundwater can be encountered throughout the mining process and needs to be diverted and disposed of due to its contamination. Very high amounts of fuel and electricity are consumed in powering equipment and transportation of personnel and materials.

The main objective of extraction is the output of concentrated metals and diamonds. Other outputs that are involved include: air emissions, waste water and solid waste. According to Environment Canada, the mining sector in Canada released 15700 Kt CO₂ equivalent of GHG (CO₂, NO_x, SO₂) in 2003.¹² Other air contaminants that are associated with the gold and base metals mining sector include: cadmium, mercury, nickel, lead, arsenic and chromium.¹³ Waste water and water contaminant release is a major concern for the mining industry. The types of contaminants released vary depending on the type of metal being mined. For gold mining, water contaminants may include Arsenic and Mercury.¹⁴ For base metals mining, the contaminants released can include: cadmium, mercury, nickel, and lead.¹⁵ When underground mining for gold or base metals encounters groundwater, the oxidation of the sulphur-bearing rocks can cause the release of H₂SO₄ (acid mine drainage) into the groundwater.¹⁶ There are massive amounts of solid waste that result from the excavation process in the mining industry. All overburden, including top-soil and vegetation, must be removed in order to commence surface mining. Also, waste rock must be removed from the mine and disposed of. An economical grade for a diamond mine is in the range of 5 carats per ton, according to Dr. J. Findlay,¹⁷ therefore leaving the majority of the rock as waste.

Surface and groundwater contamination can occur at various stages of the extraction phase. The contamination can occur from slow seepage of contaminants due to poorly constructed waste storage facilities, by acid mine drainage, or by catastrophic failure of storage facilities of tailings and other waste products¹⁸. Local air quality can be greatly affected by the release of contaminants into the air and can have major implications to human and ecosystem health. The extensive surface area disturbance and land resources required for surface mining can have serious implications for biodiversity and ecosystem degradation if reclamation efforts are unable to restore an area to it’s original state (e.g. draining of Lac de Gras, NWT, Canada).¹⁹ The emission of greenhouse gases in the extraction phase can be a significant contributor to climate change.

Phase 3: Processing

The processing phase of the life cycle assessment involves the further refining of concentrated metals and diamonds of the mining process. Processing covers all aspects of the separation and concentration of the metals as well as diamond cutting and polishing. The most complex phase is the separation of metal ores and diamonds from surrounding waste rock materials. It is conducted using a variety of processes.

The base metals that make up a gold ring, which form an alloy with gold, are silver, nickel, zinc, and copper. In order to extract metal ores (silver and gold) from the waste rock, several possible extraction methods can be used. Some of the processes used to separate gold from surrounding rock are: gravity, floatation, comminution, or magnetic processes. All of these separation processes require the use of water.²⁰

Floating agents are often toxic, but are hydrolytically decomposed while still in the processing plant. Ore extraction is often done with either heat or water. The water-based separation process—hydrometallurgy— is becoming increasingly common. Hydrometallurgy uses leaching liquids that are often acids, alkalis, salts, or other solvents, and the resulting waste water is polluted with remnants of these chemicals.²¹

Other methods involve large quantities of cyanide. One way of extracting gold from ore is to spray the ore with cyanide and induce the gold leaching out of the ore. Many mines use several tons of cyanide each day, and this cyanide-contaminated waste is usually abandoned. To put this into perspective, a rice-grain-sized amount of cyanide is fatal, and to extract enough gold for a single wedding band, 18 tons of waste-ore are produced. Today, the efficiency of the gold industry is very low: 0.00001 percent of ore (by weight) can be refined into gold; everything else is waste. Comparatively, copper mining performs little better, resulting in 0.51 percent of weight proportion of ore actually being usable copper. The amount of waste from the mining industry in the US is 9 times the amount produced by US towns and cities combined. “In 2001, the most recent year for which data were available, metals mines produced 1,300 tons of toxic waste—46 percent of the total for all US industry combined—including 96 percent of all reported arsenic emissions, and 76 percent of all lead emissions.”²² Some of these toxic substances are naturally occurring, but are disturbed and released by the mining process, whereas others are intentionally added to the gold leaching process. The efficiency of mining and consumer awareness of their demands for metals has not changed as demonstrated by the continued growth of gold on the NY Stock Exchange.

After the separation process, metal is melted into blocks at almost 100 percent purity, and is then sold to buyers who melt parts of the gold blocks to make the gold ring. This process uses intense heat and therefore consumes large amounts of electrical energy, which, depending on the region, is generated with either water or fuel.

Rough diamonds, being the hardest material in the world, can only be effectively cut and polished using other diamonds and diamond film. Other substances, such as silica, are sometimes used in the cutting and polishing process; however diamonds are the tool of choice.²³

The inputs into the ore and diamond processing systems are: electricity used to run the processing facility, and the fuels associated with transportation to the processing facility (if the processing takes place outside of the mining area); the chemicals used to separate rough diamonds, gold and metals from surrounding waste rock material; and the water used in the separation processes.

The chemicals used in solutions designed to dissolve the “waste rock material” surrounding gold or diamonds can be released along with the sludge into the environment. The base-metal production process produces a lot of waste. Some examples of the waste that results from the extraction of solid metals include: large amounts of solids (gypsum, jarosite, slag, etc.), air and water pollutants (e.g. CO₂, SO₂, NO_x , Cd, Ni, As, Pb.²⁴

The environmental impacts associated with the processing of the metals and diamonds are airborne pollutants and water contamination. Airborne pollutants are associated with acid rain and the greenhouse effect. Waterborne pollutants are equally damaging, as they often reach the groundwater and can contaminate aquifers and other aquatic systems that are otherwise unassociated with the processing system.