Very interesting article on17 Oct 2018 07:43
block caving -
Underground Block Caving: A Guide for Investors :Investing News Network - April 16th, 2013
With the discovery of near-surface mineral deposits declining, exploring for deep-seated deposits and finding innovative ways to mine them is the solution to the ever-growing need for metals.
For example, Rio Tinto (ASX:RIO,LSE:RIO,NYSE:RIO) is transitioning from open-pit to underground mining and estimates that within 10 years, about 40 percent of its copper production will come from underground mining operations. It is estimated that by 2018, about 50 percent of the world’s ore production will come from underground mines.
Two of the world’s largest copper mines will soon move underground. The Grasberg mine in Indonesia, operated by Freeport-McMoRan Copper & Gold (NYSE:FCX), will reach its open-pit limit by 2016, while Codelco’s Chuquicamata mine in Chile is expected to do the same in 2018.
Underground mining of massive, low-grade mineralized ore bodies has been carried out for decades, but in total there have been fewer than 20 block-caving mines. In most cases, this type of underground bulk mining has occurred in order to follow mineralization at depth after the exhaustion of open-pit ore.
Bulk-mining methods are a necessary component of economically mining massive, low-grade porphyry copper, gold, molybdenum and diamond deposits, and block caving is the method of choice. The process is suitable for the mining of near-vertical, compact and highly fissured ore bodies.
By analyzing the advantages and disadvantages of the block-cave mining method, investors can understand the risk profile of this type of operation and can select the companies that are most likely to succeed in mining these huge deposits.
Capital-intensive operation
The block-cave mining method is capital intensive and can cost anywhere between $2 and $10 billion. While that is comparable to the cost of starting an open-pit mining operation, block caving takes significantly longer, usually in the 15- to 20-year range. For example, Freeport’s Deep Mill Level Zone underground mine is expected to be fully developed over 12 years.
Another factor that differentiates block caving from open-pit mining operations is that for a block-caving operation, on average, 70 percent of capex is spent before any revenue is generated.
Long lead times and high capital expenditures mean that block caving carries certain risks for investors, including: geopolitical risk, long-term commodity prices and cost inflation.
cont..