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Environmental Hazard: Turning Tailings Trash To Treasure In South African Mines

Environmental Hazard: Turning Tailings Trash To Treasure In South African Mines

Tailings — the environmentally harmful leftovers after mining ore has been chemically treated and processed — are attracting investment from entrepreneurs using new technology to find the precious metal that got left over the first time, according to a report in Mining Weekly.

South Africa-based mining project company DRA said it sees potential in retreating gold tailings and also in underground gold deposits that are still rated in the pennyweight-per-ton measure of the pioneering past.

Tailings are the ground-up rock and chemicals generated in a mine processing plant. The unrecoverable metals and minerals are discharged, usually in slurry form, into storage areas or dams, along with chemicals, organics and water. The methods of handling and storing tailings are a growing environmental concern as environmental regulations get stricter, according to Tailings.

Toxic leftovers from gold mining operations can threaten the environment and health of nearby communities if acids leach into groundwater. Valuable minerals left behind in the residue also leach out and are lost, Investing News reported.

Entrepreneurs are being encouraged to develop tailings dams thanks in part to improved gold price in both dollars and rand, according to Mining Weekly.

“On the surface, there are huge opportunities,” said DRA global executive process Glenn Bezuidenhout. Shaking the dust off pennyweight plans of old could also unearth gold treasure, he added.

Pennyweight is a troy weight unit used to measure weights of precious metals and gemstones. A regular ounce is 28.35 grams, while a troy ounce is 31.1 grams. The weights are close, but the difference becomes very noticeable when you’re trading in larger quantities of precious metals, according to JMBullion.

Gold pioneers of early mining often missed gold that was invisible to the naked eye, said James Anderson, CEO of Australia-based mineral exploration company Alt Resources. South Africans are beginning to wonder what gold treasures are left behind in the pennyweight-rated areas of the Witwatersrand.

DRA says it serves as the technical arm for entrepreneurs — often with external funding sources — who want to extract gold from tailings and old mines.

Recycling tailings can be prohibitively expensive for high-tonnage processes, but the right technology can bring down costs, according to DRA.

De Beers Consolidated Mines figured out a way to extract overlooked diamonds from 360 million tons of old tailings surrounding the Kimberley mines in South Africa, Accelerating Science reported. Thanks to advances in separating, sorting, and crushing equipment, tiny diamonds can be recovered from the residue of the original diamond-bearing ore, Rapaport Magazine reported. De Beers recovered 815,036 carats of diamonds from 6,133,799 tons of tailings in 2013 and expects to continue operations beyond 2030.

Tailings may turn out to be a viable source for rare earth elements. Extremely difficult and expensive to mine, they are critical components in consumer electronics such as TVs, computers, cameras, mobile phones, catalytic converters and metal alloys. Discarded mine tailings may yield significant amounts of rare earth elements using modern extraction techniques, according to ABC News, which reported findings from the U.S. Geological Survey.

Tailings reprocessing is gaining traction in South Africa both for economic and environmental reasons, Accelerating Science reported:

DRD Gold is one of the first South African companies to abandon traditional mining to focus on extracting gold from tailings. New technology allows the company to recover up to 40 percent of the gold left in particle form in tailings. DRD Gold extracted 33,600 ounces of gold, worth nearly US$40 million, in the last quarter of 2013.

Mintails, a mine tailings processor, has developed new technology to process 350,000 tons of slimes from its extensive tailings resources. It expects to recover 58 kilograms of gold per month, and has enough slimes to last until 2025.

Goldfields has also developed new technology for a tailings retreatment plant, and processes 12,000 tons of current tailings and 88,000 tons of old tailings a month.

To accurately identify minerals within tailings, geologists turn to analytical technologies including both laboratory and portable X-ray fluorescence instruments. Portable instrument analyzers provide fast, accurate analysis of tailings to quickly and easily gauge the efficiency of extraction and enrichment processes. The real-time assay data provided by a portable analyzer allows for timely process adjustments, improving productivity and reducing the need for reprocessing.