Mount Polley Mining Corporation was future ready when the federal government published new regulations amending the Metal Mining Effluent Regulations (MMER) earlier this week.
The federal regulations, now known as the Metal and Diamond Mining Effluent Regulations (MDMER) were amended in 2018 and contain several tough new provisions that came into effect on June 1st, 2021.
For several years Mount Polley has proactively been monitoring its treated water discharge for the substances which are controlled in the new regulations and has also been testing for toxicity as is now required by the MDMER.
Toxicity testing using the water flea “Daphnia magna” has demonstrated that Mount Polley’s treated water discharge has been consistently non-toxic to this crustacean.
Daphnia magna, a commonly occurring organism in British Columbia and one that is a food source for certain fish, is particularly sensitive to dissolved copper. Dissolved copper is the “bioavailable” form of copper and Mount Polley is pleased that its water management strategy has successfully mitigated these effects.
Magnetite (also magnet iron, magnet iron stone, iron oxide, or iron (II, III) oxide) is the most stable iron oxide with high resistance to acids and alkalis. It has a cubic crystal system and a chemical molecular formula Fe3O4. One of the iron ions is divalent. The other two are trivalent, so Magnetite is also referred to as iron (II, III) oxide. It has a ‘Mohs’ hardness of 5.5 to 6.5, a black color, a line color, and a matte metallic sheen.
History of magnetite mining
Magnetite is one of the most powerful magnetic minerals. When the temperature falls below 578°C, the magnetization is mostly aligned in the earth’s magnetic field direction. A remnant magnetic polarization of the order of magnitude 500 nT results. In this way, magnetite crystals can preserve the direction of the earth’s magnetic field at the time of their formation.
The investigation of the direction of magnetization of lava rock (basalt) led geologists to observe that in the distant past, the magnetic polarity of the earth must have reversed from time to time. Due to its excellent magnetic properties, Magnetite is still used today in the construction of compasses. As a color pigment, it bears the name iron oxide black.
The name magnet emerged from the Latin name form magnetem (from nominative magnes – magnet). The medieval mineral name Magneteisenstein and the name Magnetit were introduced by Wilhelm Haidinger in 1845.
According to Greek legend, the shepherd Magnes is said to have been the first to find a natural stone with magnetic properties. The shepherd found the stone on Mount Ida when his shoe-heel stuck to the ground.
Another possible origin of the name refers to the Greek landscape Magnesia. Georgius Agricola (1494-1555) used the term “magnetic stone” in his well-known work De Re Metallica in 1550 as an ingredient for glass production.
The reference to the stone magnes, named after a shepherd of the same name, can be found in works by the Roman writer Pliny, the Elder. Pliny distinguished two types of magnes; a “male” and a “female,” of which only the male had the power to attract iron and thus corresponded to the actual Magnetite. “Female” magnesite was probably manganese ore, similar to the “male” in appearance.
The mineral might have also been named after Magnesia, a landscape in Thessaly or the city of Magnesia. It is also possible that the name Magnetite comes from other Greek or Asia Minor places of the same name, in which iron ore chunks with magnetic properties were found over 2500 years ago.
Magnetite occurs in solid or granular form and also as crystals. The latter are often octahedral in shape, so each has eight triangular boundary surfaces. It is a ubiquitous mineral, but it is rarely the main component of an iron rock.
Magnetite is found in numerous igneous rocks such as basalt, diabase, and gabbro in metamorphic rocks. Its hardness means that Magnetite remains intact as sand in river sediments despite weathering processes.
Most of the Canadian Magnetite comes from the Labrador Trough region, on the border between Newfoundland and Quebec and Labrador. Vast deposits of Magnetite can be found in Nunavut, Faraday Township, Hastings County, Ontario, and Outaouais, Québec, Canada. Magnetite deposits are mined in British Columbia at Mount Polley.
Dense Media Separation
Magnetite can be used in industry as a giant magnet. This has applications for sorting valuable materials from others in order to extract value. Those that panned for gold used pans, water, and agitation to remove dirt and debris from valuable nuggets of the valuable ore. Recyclers use magnetite in huge magets to sort valuable scrap metal from less valuable material. Magnetite mining helps the world extract value in an efficient way, whether from raw material or to repurpose discarded material in a green and environmentally friendly manner.
Dense Media Separation has its origins in cleaning coal. Finer coal material is separated from impurities making the energy derived from coal mining cleaner and more efficient.
Dense Media Separation is used in recycling industries to sort scrap metal. This is useful to give valuable material new life in everyday products from smartphones to electric vehicles. Magnetite makes recycling much more efficient, reducing the market price for recycled metals, allowing it to compete with newly mined metals in manufacturing.
Potash mining is a significant industry in Canada, particularly in the province of Saskatchewan. Potash is primarily used in fertilizer to more cheaply and efficiently feed a hungry world. Magetite, through the process of dense media separation, is used to purify extracted potash. Potash is a mixture of potassium chloride (KCl) and sodium chloride (NaCl). Magnetite is used in dense media separation in the potash extraction to remove NaCl from solution, leaving the valuable KCl behind.
Along with hematite, Magnetite is one of the essential iron ore. At 72 %, iron has the highest content of this metal. The term iron oxide black means finely ground Magnetite.
Magnetite plays an essential role in the electrical industry. The occurrence of magnetic ores in rocks such as Magnetite or ulvite enables geological studies to be carried out on the earth’s magnetic field orientation.
Due to the 100 % spin polarization of the charge carriers predicted by theory, Magnetite is also traded as a hot candidate for spin valves in spin electronics.
As a building material
Magnetite is used in the construction industry as a naturally granular aggregate with a high bulk density (4.65 to 4.80 kg/dm 3 ) for heavy concrete and structural radiation protection. Thanks to the heavy mineral, the building material can help to attain a solid concrete density of more than 3.2 t/m3; and is helpful in the construction of hospital radiology units.
Radiation protection concrete achieves a shielding function through its mass, but an aggregate with radiation-absorbing properties such as Magnetite increases the protective effect.
Magnetite in jewelry
Classic jewelry clasps are often extremely filigree and, therefore, difficult to close. Magnetic jewelry clasps provide a remedy; they enable necklaces and bracelets to be easily closed. The strong magnets ensure a firm hold. To open the chain or strap, wearers simply have to slide two locking parts sideways.
Industries use natural iron oxide minerals because they can keep the heat very efficiently. They use Magnetite in heat blocks in night storage heaters. Magnetite facilitates more extensive storage of thermal heat much more sustainably compared to other materials.
Magnetite is used in foundry metal protection
The mineral helps to prevent surface defects in metal fixtures in foundries. Natural mineral magnetite where it crashed into a pure, dry, and fine powder that’s used to protected casted metals.
Magnetic therapeutic beliefs in ancient times
Magnetism has been used traditional therapies for thousands of years, though modern science disputes therapeutic effect in placebo trials. The Greeks used magnetism in ancient treatments in 5th century BC. In China, magnets have been integrated into traditional therapy for over 2000 years, magnetism was also in traditional therapeutics in India and ancient Egypt to heal broken bones and other ailments.
Hippocrates described their healing power in the same way as the legendary doctor Paracelsus, who recommended treatments with magnets. Even during this time, women and men wore jewelry made from magnetic ores.
In ancient times magnetite mining became a major economic activity in the Thessalian city of Magnesia. Today, like the ancient Greeks, Canada has a reputation as a leading mining nation with the minerals sector as a core part of the economy. Magnetite mining supports jobs and increases economic growth in provinces and territories where it is mined along with broader benefits to Canada’s national economic output.
Gold is the chemical element with the symbol ‘Au’ on the periodic table of elements. It has been prized for its appearance, use, and value since its discovery by peoples long ago, as far back as 4000 B.C.
The yellow metal is worth so much due to its rarity, its appearance, how easily it melts and can be manipulated, its lack of oxidation or tarnishing. It is also valued for its density and durability. All of these contribute to the allure and desirability of this metal. It really is heavy! Do you think you could walk away with a cubic foot of gold if you found it? A cubic foot of gold weighs approximately 1,206 pounds!
Today you can find gold at jewelry stores, in collected coins, in edible form, and in many other places. Let’s take a tour and discover more about the history of gold mining in Canada, the history of gold, uses for gold, and more about this precious metal.
Gold Mining in Canada
Canada mines a variety of metals and minerals for sale on the global market, gold among them. Gold mining in Canada occurs in nine provinces/territories. In terms of the value of production, it is Canada’s highest valued commodity. Canada joins Russia, the United States, Australia and China as the top gold mining nations of the world.
Gold can be found in many regions in Canada. It was first found in 1823 in Québec along the shores of the Rivière Chaudière. Gold was then found in British Columbia’s Fraser River in its sands in 1858 after ‘rushes’ in California and Australia. This began the Cariboo Gold Rush. It was followed by the Yukon’s Klondike Gold Rush four decades later, which started one of Canada’s most productive eras of mining gold. However, the first to mine and prospect for gold in North America were the Aboriginal peoples.
Many gold mining camps were established in the early 1900s. Gold fever was rampant! Canada expanded its gold production capacity when the second World War started to meet wartime expenses. That capacity reached 166 tons in 1941 – its high – but went down dramatically due to the war. Production dropped in the 1970s in Canada due to production costs, but gold price increases encouraged growth and development. Other discoveries and development in the 1980s returned gold as important to the nation’s economy, and today the majority of Canadian gold production is derived from open-pit or hard-rock underground mines, with the rest from placer mining and base-metal mines.
Of all the minerals mined in Canada, gold is the most valuable. In 2018, it carried with it a $9.6 billion production value. Of the gold that was mined for production in Canada that same year, Quebec and Ontario were the largest contributors, making up over 75% of its mined production. The total estimated value for Canadian-exported gold in 2018 stands at $17.3 billion.
That same year, gold mines in Canada were able to produce around 183 tons of the precious metal, a substantial increase from nine years earlier when mined production of this metal stood at 88%. The Québec, Ontario, Nunavut, British Columbia, and the Atlantic region also experienced production increases. In 2018, Canada also generated income from gold in concentrates and metal ores of $806.7 million, an increase of $52.7 million from the year before. Gold mining companies in Canada made up over 20% of the mining sector’s output for the country. Overall the mining industry for gold in Canada is thriving and a productive part of the national economy.
The Bullion Pit was once called the Largest Hydraulic Placer Mine in the World, measuring over 3 km in length, 800 ft wide, and over 400 ft deep. The Bullion Pit Mine was an awe-inspiring wonder of man’s tenacity for extracting wealth from the ground in his hunt for gold. Located 5 kms west of Likely, the mine was in operation from 1892 to 1942.
However, over its lifetime, the Bullion Pit Mine produced over 175,644 ounces of gold, at today’s prices would be almost $400 million ($CAD).
The History of Gold
Early Discovery of Gold
According to historians at the U.S. National Mining Association, cultures were using gold in Eastern Europe for creating decorative objects as far back as 4000 B.C. In the years that followed, it is believed that gold was solely used for making jewelry or idols that could be worshipped.
Around 1500 B.C., Egypt’s empire had already made plenty of profit from Nubia, its region known for producing gold. It was at this time that the empire elected to make the precious metal their official medium of exchange when it came to matters of international trade. They also created the 11.3 gram shekel coin, which became the Middle East’s standard unit of measure and was created from electrum, an alloy of two parts gold and one part silver.
At the same time, the Babylonians discovered fire assay, a method for testing gold purity that is so effective that it continues to be used in modern times. The Egyptians would find in 1200 B.C. that they were able to use other metals to alloy gold, imparting strength and even being able to color it differently with various colour pigments. The Egyptians also were working on lost-wax casting, a method to create sculptures that is still in use.
Asia Minor’s kingdom of Lydia would mint their first gold coins in 560 B.C. with coins made out of pure gold. The Greeks had also done their fair share of mining from Gibraltar to Egypt and Asia Minor. The Romans also were on the hunt for gold, and would mint their own gold coins in 50 B.C. while advancing the technology and scientific approach to mining for gold significantly. The coins were named Aureus, deriving from ‘Aurum’, the word for gold in Latin.
Further on in the history of gold, when William became King of England and the first Norman king in 1066 A.D., his triumph ushered in a new English system of currency along with it. Now currency would be based on metallic coins, which led to the use of the terms pence, shillings, and pounds (one pound equating to one pound of sterling silver).
In 1284, Great Britain would issue the Florin, a gold coin and its first for the nation. In Italy, the Ducat was issued in the Republic of Florence. The gold coin would skyrocket in popularity, becoming the world’s most popular form of gold currency at the moment and through the next five hundred years.
The first gold coin to be produced in the United States was made by Ephraim Brasher, a goldsmith, in 1787. The American government would pass the Coinage Act in 1792, which led to the United States being placed on a standard of silver and gold.
In 1848, gold flakes were discovered in a Californian stream by John Marshall. This was the start of what would go down in history as the California Gold Rush, where prospectors flocked to the state to try and find their fortune in gold. While some struck it rich, for many, a grand fortune never panned out. The movement did, however, help to get the West settled and added to the state’s population for a time.
In 1976 the government left the gold standard and changed over to a basis of fiat money instead. Over the years, many countries have used gold as part of its currency, monetary reserves, and commemorative or specific coins.
Industrial Uses for Gold
Gold is not only used for luxury or decorative items – it has industrial uses as well. Gold is used to make electronics and a variety of other goods. It is a fantastic conductor and small amounts can be used to carry a current, while also having the benefit of not corroding. That and other qualities, such as its malleability and purity, makes it a valued component, ingredient, or main element for many products.
Various industrial uses for gold include:
Electronics and electronic components
Computers, memory chips
Space vehicles, space circuitry (conductor, connector, mechanical lubricant)
Gold in Jewelry and Luxury Items
The use of gold in luxury items and as a material for jewelry has gone back centuries and continues to this day. Gold has always been an attractive choice for all things ornamental or decorative, from objects such as jewelry to other symbols of status. In modern times, roughly 78% of gold that is consumed annually is for the manufacture of jewelry.
Gold is ideal for making jewelry for many reasons. Its yellow color, its resistance to tarnishing, the high luster, and its malleability or ease of being cast into shapes all help this precious metal become selected as a frequent choice for jewelry manufacture. Its high value and tradition as an attractive and expensive jewelry metal makes it a desirable component for any piece, and for many objects of importance, gold is expected to be used.
Pure gold is beautiful but also very soft, so it is often alloyed with metals like platinum, copper, and silver. For the creation of luxury items and jewelry, an alloy is frequently used of gold and another metal if it is necessary or beneficial. These alloys also will alter the final color and can produce yellow gold, white gold, rose gold, or gold with shades of peach, black, or green.
Gold leaf and gold gilding are also frequently used in luxury items and applications. The opulent forms of gold are used in external building decoration, in photo or painting frames, furniture, decorative application to surfaces, luxury purses, jewelry, home interiors, and in many more applications. The choice of gold as a luxury item and in the manufacture of jewelry will result in a product that is of the highest quality.
Gold As a Reserve
Gold was used by countries as a way to provide a guarantee to others. Held in the bank during the times of the gold standard, it was a store of value for the nation. While today countries have largely moved off the gold standard, central banks continue to store ample gold reserves, with more being added yearly.
The U.S. has the greatest gold reserve at over 8,000 metric tons, worth hundreds of billions of dollars It is followed by Germany, Italy, and France. Other countries continue to add to their own reserves. In addition, entities such as the European Central Bank and the IMF have their own gold holdings. Developed countries keep these gold reserves because of their central bank policy and their guaranteed worth regardless of circumstance. Gold serves to protect against economic events as a fail-safe policy, while simultaneously supporting the value of currency.
Silver is a soft metal with many valuable properties that make it a desirable resource for reasons both practical and luxurious. The chemical element goes by the ‘Ag’ symbol on the periodic table of elements and comes with a melting point of 962°C. It is superior to other metals in that it exhibits high levels of thermal conductivity, electrical conductivity, and metal reflectivity. Read on to find out more about this highly prized metal in its uses, history, and application and influence regarding the modern world.
Silver Mining in Canada
Canada has a robust mining industry that produces many minerals, silver among them. Canada produces gold, coal, potash, iron ore, copper, and silver, among other minerals mined. Canada placed fourteenth on a list of countries producing silver in 2017, producing 12.7 million ounces. Global production of silver in 2017 was 852.1 million ounces.
Canada features many concentrated production areas where mines are located and silver mining in Canada takes place, mainly in BC, Ontario, New Brunswick and Québec. Every year, Canada is able to produce over a thousand tons of silver to bring to market.
British Columbia is home to a number of Canadian mining companies and has a storied history of mining for this precious metal. The Sullivan lead-zinc-silver mine used to be one of the world’s largest producing 280 million ounces of silver while the mine was in production from 1909 through 2001.
Much of Canada’s silver production comes from mining as a byproduct; National Resources Canada states that most Canadian mines are polymetallic. As a result, silver is derived frequently from ores made out of copper and nickel, copper and zinc, and gold and lead. Besides ores, silver can be recovered from various recycled materials. Silver mining continues to be a source of income for the mining companies as well as having the effect of boosting Canada’s GDP.
Uses for Silver
This beautiful metal with the white luster is used in many ways and for many things. The metal is resistant to corrosion, and its malleable nature means that it can be worked with in different ways, whether being rolled, drawn out into a finer form, or other practical methods. Here are some of the most practical and popular uses,
Utensils and silverware
Industrial materials and applications
Water purification systems
Silver plating for art
Coins and currency
Medical products, such as surgical pins and plates
Photographic film, paper (accounts for nearly a quarter of fabrication silver demand)
Silver is the most conductive element on the periodic table of elements, followed by copper and then by gold. Silver owes its conductivity to its single valence electron, moving freely between atoms of silver. Due to the high price of silver, it is not typically used in wiring but can be found in high value electronics. Copper is more typically used as its price and conductivity are suitably matched for use in household appliances.
History of Silver
Silver has long been prized by people around the world. The metal is easy to work with, can be used for different purposes, and it’s attractive. Silver was used to make up currency such as coins and was used in utensils, ornaments, jewelry, decorations, and so much more through the centuries. Now, a brief summary of the history of silver.
Ancient peoples used silver for many things. It was used for jewelry, for eating utensils, and for ornamental purposes. Silver mining can be traced back to 3,000 B.C. in Greece and Turkey. Ancient people were able to refine the element by heating silver ore, using a cupellation process to blow air over it. As a result, base metals would oxidize and separate, leaving the silver to be then worked further.
In 1492, the Europeans arrived at what they called the New World. It was then that the explorers from Spain realized that South America was home to a fortune. It had veins of silver as well as silver ore ready to be exploited. The Spanish mined the silver and from 1500 to 1800, the majority of silver produced in the world would come from Bolivia, Mexico, and Peru (85%).
With so many practical industrial purposes, silver in industry was an important part of the Industrial Revolution. Around 1750, an age was beginning, powered by the fossil fuels that provided the energy that pushed it forward. Machines and factories could now run on the large amounts of oil, coal, and natural gas that were being produced. Silver’s malleability gave it a variety of uses and meant that it could make up different products on its own or as part of its alloy. It was also used in a monetary application as well, in currency and in national reserves.
Silver is especially an important element in modern times. Many countries produce silver, including the United States, Mexico, Peru, Canada, Australia, China, Poland, Russia, Bolivia, and Chile, to name a few of the large-scale producers. The metal continues to be a popular material used to make up everything from tableware and silverware to jewelry, mirrors, alloys, batteries, and more.
Silver in Jewelry and Luxury Goods
Silver finds practical and aesthetic use in silver jewelry as well as luxury goods. These products also serve as a large portion of the demand for silver. Silverware, jewelry and industrial use account for about 70% of the demand for the metal’s fabrication. Since pure silver is actually too soft to make up the entirety of the product, sterling silver is often a practical choice. The alloy is made up of 92.5% silver, 7.5% copper, with variations or different metals sometimes used.
Silver is a frequent choice for many types of jewelry. Necklaces, earrings, bracelets, bangles, and more are usually offered in two options, silver or gold. But silver is also increasingly starting to prove useful when it comes to being incorporated into clothing. The antimicrobial properties of this metal means that silver nanoparticles may be woven into clothing, which discourages bacterial build up and provides a luxury material that is more breathable and comfortable to wear.
Other luxury goods that feature silver are electronics. Electronics frequently use silver as part of their wiring. It is also a necessary ingredient for photographic film, which accounts for a large range of the demand for the silver (25%). Silver jewelry and similar aesthetic items also make up a smaller but substantial demand for silver production. The element is also used in art to make up silver plating.
Silver as a Reserve Commodity
Silver is in demand as a reserve commodity much like gold, and has been used to back currencies in the past. Silver reserves are used as countries as a type of security. Silver continues to hold value, thus countries set silver aside. In 2019, Peru had a silver reserve that had reached 120,000 tons.
What makes gold such an excellent mineral for jewelry making? Special properties of gold make it perfect for manufacturing jewelry, including very high luster; desirable yellow color; tarnish resistance; ability to be drawn into wires, hammered into sheets, or cast into shapes. These are all properties of an attractive metal that is easily worked into beautiful objects. Another extremely important factor that demands the use of gold as a jewelry metal is tradition. Important objects are expected to be made from gold.
Gold is mined in 9 Canadian provinces and territories, and is the highest valued commodity produced in Canada by value of production. Demand for gold production continues to grow each year. In fact, half of the global demand for gold is used for jewelry production.
Nickel also plays an important role in fashion. Nickel is used to make earrings – and the posts assembled into pierced ears – necklaces, bracelets and chains, anklets, finger rings, wrist-watch cases, watch straps, rivet buttons, rivets, zippers and metal marks.
Indium is “the everyday metal you never see”. According to the USGS, Canada is one of the top six producers of indium in the world. In fact, Teck is a key contributor as one of the largest single source producers of indium in the world.
So what is Indium used in? This is best explained by a US publication, Mining News North:
“If you are reading this article on your computer, tablet or phone, you are almost certainly looking through indium, and if that devise happens to be a touchscreen, you have the unique properties of this critical mineral to thank as you scroll down to read more about indium and where it can be found in Alaska.
This is because indium-tin oxide is used as a transparent conducting film applied to virtually every flat-panel display and touchscreen on the market. This thin coating transforms incoming electrical data into an optical form.
When it comes to the combination of characteristics required for this widely used application – transparency; electrical conductivity; strong adherence to glass; corrosion resistance; and chemical and mechanical stability – indium-tin oxide has no equal.”
And mining plays a big role in making the sport possible.
Hockey sticks, skates and nets are all made of materials mined in Canada.
The most popular hockey sticks are one-piece composite sticks — typically of graphite, though unique materials such as Kevlar and titanium are also used, and occasionally coatings such as nickel cobalt are applied for added strength.
Blades on hockey skates are generally made of tempered steel and coated with a high-quality chrome. Some blade manufacturers may add titanium to the metal.
Graphite, titanium, steel, chrome, nickel and cobalt are all mined in Canada. In fact, Nickel was first discovered in Canada in 1883, and began being mined in the 1890s.
Today, Canada is one of the world’s five top five nickel-producing countries.
Michael Goehring, CEO, Mining Association of BC discusses mining’s important role in the green economy.
“BC is a hotbed of innovation, so our industry is working closely with BC’ tech sector so we can conserve more, waste less, and reduce our environmental footprint.”
“The minerals and metals that BC produces – copper, silver, gold, steel-making coal, aluminum, molybdenum – they are all essential to a low-carbon future. An electric vehicle takes four times as much copper as a traditional internal combustion vehicle. You can’t make solar panels without silver. And you can’t transmit power from solar panels without copper. Our mineral sand metals are essential to a low carbon future.”
“We now know, in BC, our steel-making coal – which is critical to renewable energy infrastructure – wind mills, for example, has half the GHG emissions intensity as our competitors in Australia. BC’s Copper has about 40-50% less GHG emissions than copper from Chile. Our industry has been reducing its GHGs for several decades. The real driver is our clean energy, driven out of our hydroelectric assets.”
In the Mount Polley
Mine, run-of-mine ore from the open pits and underground is hauled to the
crusher. The crusher has three stages of
crushing involving five crushers, twenty conveyors and four sets of screens. Ore is dumped by the surface mining fleet
into the feed pocket of the primary gyratory crusher, and is then crushed in
three stages to produce a product at finer than 16 mm for the grinding circuit.
Periodically, the crusher also used for the production of aggregates used in
tailings construction and other tasks.
The grinding circuit
consists of two parallel rod mill/ball mill circuits and a pebble mill circuit.
Crusher product is first split between two rod mills where water is added to
form slurries. The rod mill discharge is
pumped to the primary hydrocyclones that classify the particles by size. The larger particles flow to feed the ball
mills while the fine particles report to two flash flotation cells. The ball
mills are in “closed circuit”, meaning that the discharge is pumped to the
classifying units (primary hydrocyclones) and the particles will not pass to
the next grinding stage until they are fine enough to feed through the flash
flotation cells. The underflow from the
flash flotation cells is pumped to the secondary hydrocyclones, the flash
flotation product can report directly to the concentrate circuit or to regrind
for further upgrading.
The coarse particles
classified by the secondary hydrocyclones reports to three pebble mills for
further size reduction. The pebble mills are in “closed circuit” with the
secondary hydrocyclones and product that is sized at 65% finer than 200-mesh is
fed to the flotation circuit. Pebbles obtained from the triple deck screen in
the crusher are used as grinding media in the pebble mills.
The flotation circuit
separates the valuable minerals from the rest of the crushed rocks. With the
addition of reagents, the valuable minerals, mostly in the form of sulphide
minerals chalcopyrite and bornite, are separated by flotation and are collected
and upgraded to produce a concentrate. Initial separation is completed in a
rougher/scavenger circuit, where the remaining minerals are discarded as
tailings (which flow by gravity to the Tailings Storage Facility). Rougher concentrate is reground in a regrind
mill and further upgraded in a cleaner circuit to produce the final concentrate
product. Cleaner tailings are recycled to the scavenger circuit.
The concentrate from
the flotation circuit is dewatered in two stages: the thickener settles
particles and decants water so that the settled particles form a sludge by
sedimentation and have a reduced water content of roughly 25%-30%; pressure
filtration further reduces water content to approximately 8%. The water removed
is utilized as process water. The filtered concentrate is stored in the
load-out building and loaded onto 40-tonne trucks for shipping. Tailings
materials generated by mill operations are piped via gravity to the TSF.
The broken rock in the open pit is segregated into ore and waste based on the assay of rock cuttings sourced from the blasthole production drills.
This assay analysis determines the sulphide copper percentage and gold grams per tonne for material within the vicinity of each blasthole.
The forecasted metal prices and metallurgical recovery is used to calculate copper equivalent percentage.
A forecast of mining and treatment costs establishes the mining cutoff grade and hence the material to be trucked to the plant for processing.
The plant uses three stage crushing, and conventional rod and ball mills with a flotation and dewatering circuit to produce a copper /gold concentrate.
When the mine is up-and-running, it mine moves 80,000-90,000 tonnes of material per day, the mill has a capacity to process 17,800 to 22,000 tonnes per day (tpd) of ore depending on hardness. Mount Polley concentrates are trucked to facilities at the Port of Vancouver and then shipped to overseas smelters.