Arsenic and Gold

We usually think of arsenic as a bad thing – for example, in well water and historical mine tailings - but arsenic has many important uses. In fact, the Government of Nova Scotia studied the province’s potential for mining it in 1924.

Arsenic is naturally-occurring in all rock and many areas of Nova Scotia have elevated arsenic levels, regardless of whether mining has taken place locally. Arsenic-bearing minerals are often unstable and can leach naturally into groundwater, so it is important to test wells for it regularly.

Arsenic is commonly found in the arsenic-bearing mineral arsenopyrite, which often occurs with gold in nature. Modest amounts of arsenic were sometimes recovered in the historical era in Nova Scotia, mostly at gold mines, and exported to places like Wales, Germany and Belgium. However, various challenges, including high shipping costs, lack of markets and low gold prices, prevented the establishment of a regular arsenic industry.

Because gold miners in the 1800s and early 1900s did not understand arsenic’s environmental impacts, waste rock and tailings that contained arsenic were often just left at mine sites, a practice that is obviously unacceptable today but was standard 100-150 years ago.

Because of arsenic’s association with gold deposits, the Department of Mines wrote a memo in January 1924 discussing the province’s potential to produce arsenic, which is used today in many products, including semiconductors, pharmaceuticals, agricultural chemicals and wood preservatives.

Department of Mines staff visited almost three dozen communities that had historical gold mines and concluded, “At the present time it looks as though the production of arsenic on a commercial scale in Nova Scotia will depend to a large extent on the revival of the gold mining industry which, since 1901, has steadily declined. By reviewing the factors which has contributed to this unhappy state of affairs the difficulties to be overcome in regenerating the industry will be readily apparent. Moreover, since the arsenic in the Province is largely a by-product of the gold-quartz veins its recovery will be hampered by the same general conditions as that of the precious metal.”

Only about half a dozen gold mines were active in Nova Scotia in 1923 and they “carried on operations of a desultory nature.” The memo said there were various reasons for the “depression” in the gold sector, including that many veins had already been fully extracted, a lack of plans of historical gold mines made it difficult to efficiently continue work in those areas, higher costs for things like fuel and labour and difficulty raising capital.

Since arsenic in Nova Scotia was mainly a by-product of gold mining, “…unless gold mining is miraculously revived throughout the Province the outlook cannot be considered at all promising for the inception of an arsenic industry which will be an assured and permanent success.”

The Department of Mines also studied whether historical gold tailings – what remains after ore (rock) has been crushed and processed to extract gold - could be reprocessed to extract arsenic.

The Department concluded that the concentrations of arsenic in tailings were too low for this to be economically viable. The memo argued the tailings contained, on average, less than 0.5% arsenic, but concentrates containing something like 25% arsenic would be needed. “If concentrates containing 25% arsenic could be made this would mean that approximately 50 tons of ore would have to be crushed to obtain 1 ton of concentrates.”

The average amount of ore crushed by Nova Scotian gold mines between 1913-1922 averaged 8000 tons per year. (This average dropped to only 2000 tons per year in the period from 1918-1922, indicating just how poorly the gold sector was doing at the time.) The average 8000 tons of ore per year would only produce 160 tons of arsenic concentrates, and only 50 tons of actual arsenic, worth about $13,000. The cost of the equipment needed to produce arsenic would not have been justified by the potential revenue.

Despite the Department of Mines’ pessimistic view of the province’s arsenic potential, the memo said that some gold mine operators were interested in it. For example, the owners of the Brookfield mine in Queen’s County were considering installing an arsenic-recovery plant because its ore contained 15% arsenic. Recovering arsenic was also considered at gold mines in places such as Dufferin, Montague, Moose River and Goldenville.

The memo also mentioned two sites where arsenic had been extracted for its own sake, not as a by-product of gold mining. In Meaghers Grant, Halifax County, a small amount of arsenic was mined starting in 1923 near Anderson Dickie’s house. The ore contained 35-40% arsenic but “At the present price of arsenic it is doubtful whether this property can be regarded as a source of this substance.”

Arsenic was discovered near Williamsdale, Cumberland County, in 1906 on Clifford Taylor’s farm. In 1909, the Arsenic Mining and Prospecting Company mined about 100 tons of ore and shipped 20-30 tons to Germany. F. W. Nelson of Springhill later took over the site and prospected for gold. By 1924, the mine’s shaft was 100-feet deep and Ernest Chisholm of Truro continued was working the property. Waste rock at Williamsdale also contained gold and silver. Today, a small stream near the mine shaft drains into Arsenic Brook.

No industry took proper care of the environment 100-150 years ago and mining was not an exception. However, modern mining is completely different. For example, today, waste rock is contained in engineered facilities that ensure materials like arsenic cannot impact water.

Modern tailings, usually in the form of slurry, are stored in a tailings management facility – a lined and walled area on a mine site designed to contain the tailings indefinitely. The extensive science and engineering behind tailings management protects the environment. For example, site-specific geotechnical and engineering studies are done for each tailings facility to determine the best technical option to provide containment.

Mines today can often remediate historical tailings as part of the modern mining process, often by moving them into the modern mine’s tailings facility, as was done at the modern Moose River gold mine. Scientific advancements also now create more opportunities to reprocess historical tailings to extract minerals.

Before getting operating permits, mining companies must get government approval of reclamation plans and post reclamation bonds (money in escrow, basically) that ensure funds are available to properly take care of sites. In fact, reclamation is a key part of the mining process today and progressive reclamation - reclaiming areas where extraction is complete while continuing to mine elsewhere on-site – is standard industry practice.

The Moose River gold mine in 1897.

Digging up historical tailings at the modern Moose River mine to prevent them interacting with the environment.

The modern Moose River mine's tailings management facility, where historical and modern tailings were placed.