Categories
Mining facts

Magnetite and Magnetite Mining in Canada

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.

Crystal structure of magnetite: oxygen (gray), divalent iron (green), trivalent iron (blue), iron ion in octahedron gap (light blue octahedron), iron ion in tetrahedron gap (gray tetrahedron) – Wikimedia commons

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.

Magnetite is magnetic!

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.

Illustration of Magnes the shepherd

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.

Occurrence

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
Magnetite

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.

Magnetite Uses

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.

Scrap metal recycling

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.

Potash mining

Electrical industry

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.

Wearing jewelry is helped by magentic clasps

Heat storage

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.

Categories
Community Exploration Remediation

A letter from the Mount Polley Team

Happy Holidays – we hope that everyone enjoyed a joyous holiday season and wish you all the best for 2021.

A Covid-19 update – Mount Polley employees continue to take additional precautions to minimize the risks of COVID19 transmission and illness as recommended by the Provincial Health Officer. All personnel continued to report to work in Q4.

Employees and site visitors are required to sign off on a daily COVID-19 Questionnaire before entering the site and will be turned away if showing symptoms of illness.

Mount Polley Mine: Care and Maintenance

Bulletins regarding the mines care and maintenance:

  • The environmental monitoring programs continue and are on track
  • Closure research projects continue as planned
  • Remediation of Hazeltine Creek continued at Lower Hazeltine, projected to be complete in 2021
  • Workforce consists of thirteen staff plus additional contractors
  • Site water management continues, including the near-continuous operation of the water treatment plant
  • Exploration Geological Mapping of new areas on mine site
  • CANMAG shipping magnetite

Environmental Monitoring Update

Environmental team: Matt O’Leary, Gabriel Holmes, Kala Ivens, Alicia Lalonde (DWB Consultant), Kim Sandy, Don Parsons (Corporate Office)

New Hire

Kimberly Sandy was hired on November 16 as the newest member of the Mount Polley environmental team.  She has been hired as an Environmental Technician and extensive on-site training is underway.

New ENV Permit

A new ENV permit 11678 was issued on December 31, 2020 that incorporates conditions from a previous consent order because of ongoing appeals of conditions within the permit as issued on February 1, 2020.

Quarter 4 routine monitoring activities completed:

  • Weekly WTP water quality sampling including monthly/quarterly toxicity sampling
  • Monthly water quality sampling at Hazeltine Creek 
  • Monthly & Quarterly water quality sampling of surface & mine affected waters including groundwater, mine seepage
  • Hydrological monitoring
  • Polley Lake, Bootjack Lake, & Quesnel Lake water quality sampling 
  • All critical ditches, sumps, ponds, and pipeline inspections 
  • Monthly/quarterly Waste Inspections
  • Continued investigation of unauthorized discharges and exceedances
  • Reporting—monthly, quarterly, investigations
  • Monitoring planning as per the Comprehensive Environmental Management Plan (CEMP) and ENV Permit 11678

Specialized Environmentally Related Work

During the course of the year, we enlist the help of numerous environmental consulting companies to complete some of the specialized components of the environmental monitoring done at Mount Polley Mine.  Examples include bird song surveys or benthic and invertebrate studies in the remediated areas of Hazeltine Creek.  Most of our consultants completing specialized environmental work have wrapped up their field seasons and are processing data and interpreting their field observations in preparation for delivering their reports.  Some of these reports satisfy CEMP requirements and some are stand alone studies.  The results of this work can be found in the upcoming Mount Polley Mine Annual Environmental Report.  Some of the companies that we engage with include Golder Associates Ltd, Minnow Environmental Inc., DWB Consulting Services Ltd., Ensero Solutions, and Watersmith.

Environmental monitoring is conducted in accordance with the Environmental Management Act (EMA) Permit 11678 and the approved Comprehensive Environmental Monitoring Plan (CEMP) requirements.

Snow corer for evaluating snowpack.

MPMC Water Treatment Plant (WTP) Update

In Quarter 4, the total treated water discharged to Quesnel Lake was ~1,592,581 mᵌ with an average discharge rate of ~0.2mᵌ/second.

The plant operated continuously for most of Quarter 4.  Water quality samples were collected weekly at the Water Treatment Plant (WTP) at the influent (E19) and effluent (HAD-3) sites throughout the quarter.  To further optimize the plant operations the WTP operators have been utilizing a Hanna Multiparameter Photometer to assess influent and effluent copper concentrations to help guide daily plant operations.  We are developing a data set comparing the field readings to the lab results to verify the reliability of the instrument. 

Water Treatment Plant Laboratory

Permit Exceedance

On November 11, 2020, a permit exceedance for elevated copper was observed at the WTP.  Through the course of the resulting investigation, the plant was shut down for four days, additional samples were collected (in recirculation mode), a site contact water review was completed, the source of copper was identified, plant operations and site conditions were assessed key findings were identified and operational recommendations were compiled. The plant resumed normal operation on November 27, 2020.

Bypass Request

On October 26, 2020, MPMC requested a bypass of the authorized works (the WTP) to discharge mine site contact water that is being stored in the Springer Pit without active treatment.  Through the course of the last year, the water quality in the pit has improved greatly and meets the end of pipe permit limits as indicated by the sample results taken during on-site monitoring.  This is the result of the water clarifying and passive in-situ treatment occurring in the pit.  The bypass request also included water from the Tailings Storage Facility (TSF) and the Cariboo Pit provided that they meet the end of pipe permit limits.  Significant water quality fluctuations are not expected because of the single-source nature of the bypass.  Monitoring is planned to increase in the Springer Pit to provide early warning of water quality changes and will remain at the same frequency at the end of the pipe.

Another driver for this request is to aid MPMC in eliminating surplus water currently being stored on site.  The quantity of water stored on-site currently exceeds “Best Practices” as advised by the Tailings Storage Facility Engineer of Record.  A bypass authorization will enable MPMC to increase discharge volumes while still meeting permit limits and BC Water Quality Guidelines. This will also limit year-over-year accumulation of stored water on site.  A similar bypass authorization request was submitted by MPMC in 2016 and approved by the British Columbia Ministry of Environment (MoE) on March 11, 2016.

Water Treatment Plant and Discharge Pipeline to Quesnel Lake

MPMC Water Treatment Plant (WTP) Update-Graph

Hazeltine/Edney Creek Remediation 

Remediation work was limited in Q4 to ground cover seeding and seed collection efforts.  All areas that were disturbed by the 2020 construction near Hazeltine and Edney Creek were seeded.  Additional Sitka Alder and Cattail seeds were collected for distribution.  The native ground cover seed blend that is used in the remediation is comprised of Mountain Brome, Native Red Fescue, Rocky Mountain Fescue, Bluebunch Wheatgrass, Blue Wildrye, Fireweed, and Big Leaf Lupine.

Lower Edney Creek and Secondary High Flow Channel
Newly Constructed Edney Creek Outfall to Quesnel Lake
Hazeltine Creek Reach 3
Ice Forming in Lower Edney Creek

Exploration Update

In late 2019, a comprehensive exploration program consisting of a geochemical MMI-soil sample survey and a geophysical 3D-IP survey was carried out over the Frypan/Morehead area located west and north of the Mount Polley mine. The target area is roughly 3 by 3 kilometers in size, largely till covered and shows a similar magnetic response to that obtained over the Mount Polley mine host rock of monzonite and hydrothermally altered monzonite breccia pipes. 

In June 2020, an additional 3D-IP survey was conducted over the Mount Polley mine site to identify the geophysical response of the known mineralization. 

Interpretation of the new geophysical data sets led to numerous high-priority targets both in the Frypan/Morehead area and on the mine site. 

A drill program was planned to test the new high-priority targets on and off the mine site and to expand zones of known mineralization on the mine site. The first phase of drilling was carried out at the end of 2020. 

Due to prolonged delays with assay labs, the program is waiting for results before drillings resume. 

MPMC EVENTS

Quarter 4, 2020

October 7:

Public Liaison Committee (PLC) Meeting via conference call

Upcoming

February 3, 2020

Public Liaison Committee (PLC) Meeting via conference call

Resources

imperialmetals.com

BC Mine Information Page: https://mines.nrs.gov.bc.ca/

BC Ministry of Environment Natural Resource and Enforcement Database: https://a100.gov.bc.ca/pub/ocers/searchApproved.do?submitType=menu

If you have any questions regarding the Community Update, please email Gabriel Holmes at gabriel.holmes@mountpolley.com

Categories
Mining facts

Tailings – What are they and what is in the Mount Polley tailings?

First, what are tailings?

Tailings are essentially crushed rock, and are the leftover material after the minerals containing the “elements of interest” have been removed. At Mount Polley the elements of interest are copper, gold and silver. The minerals containing the copper, gold and silver are released by crushing and grinding the mined rock down to sand and silt sized particles.

At Mount Polley, a process known as flotation is then used to separate the important copper-bearing minerals from the rest of the crushed ground rock. The remaining crushed rock is considered waste (gangue) and is what makes up the tailings. No cyanide is used at Mount Polley.

Read more about Tailings on the Mining Association of BC’s website here.

What is the in the Mount Polley tailings?
At Mount Polley, the valuable elements are copper, gold and silver and they are found most commonly in the sulphide minerals, chalcopyrite and bornite. The leftover minerals found in the waste are piped as a slurry with water to the tailings storage facility. [ref: Community Updates 2017 Issue 3; 2016 Apr Issue 2]

The rocks that are mined at Mount Polley are around 200 million years old and represent ancient volcanic rocks and magma that intruded into these rocks. The intrusive rocks host the copper, gold and silver mineralization.

Let’s talk rocks!
The rocks which host most of the ore are made up primarily of the minerals orthoclase (potassium feldspar), albite (sodium plagioclase), magnetite (iron oxide), Ca-plagioclase (calcium plagioclase), diopside (pyroxene), garnet, biotite (mica), epidote and calcite (calcium carbonate). These minerals are all common rock-forming minerals, and represent 90% of what ends up in the Mount Polley tailings pond.

Of the other 10 percent, most are also common minerals, with a minor amount of sulphide minerals, including a little bit of chalcopyrite (0.17%) that didn’t get captured in the mill and a small amount of pyrite (0.04%).

What is unusual about Mount Polley is that, when compared to many other copper deposits (and the reason why these tailings are considered by geochemists to be chemically quite benign) there is very little pyrite (iron sulphide) and a fair amount of calcite (calcium carbonate) in the tailings.

Due to this, Mount Polley’s tailings do not generate “acid rock drainage”. This is the process that happens when sulphide minerals, especially pyrite, are exposed to the atmosphere and react to form sulphuric acid, which then can leach metals out of tailings and lead to metal mobility and potential contamination.

Mount Polley’s tailings do not have this “acid rock drainage” problem, as there is very little pyrite, and calcite acts as a neutralizing agent if any of the minor amounts of sulphide in the tailings breaks down. The vast majority of the rest of the minerals in Mount Polley’s tailings does not react easily with air or water, and are very similar to natural sand.