RE: Marange Diamonds22 Aug 2018 17:34
Good post Castaway.
I'm no diamond expert but I've been looking through my notes from past bouts of analysis on it and can add, hopefully of interest, a few points:
- In terms of carats produced, the Marange field is potentially the largest alluvial diamond producing project in the world, estimated to have produced 16.9 million carats in 2013, (or 13% of global rough diamond supply), 12.0 million carats in 2012, 8.7 million carats in 2011, and 8.2 million carats in 2010.
- Marange, is technically not an alluvial deposit, nor is it a kimberlite pipe. The diamonds originated from an unknown source and were deposited by seawater into a bowl-shaped bed millions of years ago. Marange is at the northwest rim of this bowl, where the diamonds can be found under just a few meters from the surface. The grade of the rim, or reef, is also very high: one method of quantifying the value of a deposit is to measure the carats per 100 tonnes of ore. It is claimed (I got the numbers from an article in the Zim Herald) that Marange produces 4 000 carats per 100 tonnes. The numbers for Zimbabwe’s two kimberlite sites, Rio Tinto’s operation in Murowa and River Ranch, are way lower by comparison: averaging 60-80 carats and 25-30, respectively.
- About 50 miles to the southeast lies the more recently discovered Chimanimani diamond deposit, which geologists have identified as the opposite rim of this bowl. In between, the bowl deepens to some 3,000 feet. It is well recognised that this could be one of the Worlds largest deposits, - one of the biggest unknowns about the Marange diamond fields is the actual size and potential values of the deposits. Although estimates of the reserves contained in this area vary wildly, some have suggested that this bowl could be home to one of the world's richest and biggest alluvial diamond deposits ever seen.
- While the bulk of Marange diamonds are of industrial grade quality, it is anticipated that the top five percent are “very serious gems” while another five percent are “decent quality”.
- If the area was mined at a responsible rate, Marange’s output could potentially sustain three million carats a month for 14 years.
I'm sure that someone with better sector knowledge than me can confirm/correct these points but hopefully they give an idea of what we're dealing with here.