What is the reason that so few diamond mines are scheduled to come online in the near future and why is diamond considered such a finite resource? To understand, IDEX Magazine editor-in-chief Danielle Max gets to grips with the process of diamond mining and discovers just how much it takes to get a diamond mine up and running.

 

We bandy the term “mine to market” or “mine to finger” about with barely a second’s thought. But it actually takes a mammoth effort to get diamonds out of the ground and onto a person’s finger. The discovery of a diamond deposit is no guarantee of the quality of the stones it contains, and nor is there any guarantee that a diamond deposit can be viably developed into a productive mine (somewhere in the region of 12,000 kimberlite deposits have been found worldwide in the last 25 years or so, yet fewer than 1 percent have contained enough diamonds to make them economically viable). But that does not mean that people are not trying. As diamonds become even scarcer, prices of rough will skyrocket, this is why the race is on to find the next mother lode before the competition and accounts for the proliferation of so many exploration companies.  

 

Diamond Deposits

Before getting to the process of is diamond exploration, it is worth taking a step back and considering that the fact diamonds exist at all is nothing short of a miracle. Most natural diamonds are formed at high-pressure high-temperature conditions existing at depths of 140 to 190 kilometers (87 to 120 miles) in the earth’s mantle (the hot, liquid interior below the crust). It takes from 1 billion to 3.3 billion years for diamonds to be created from carbon-containing minerals, which explains why diamonds are a valuable, finite resource.

 

As if this was not enough, the correct conditions for diamond formation to happen – the correct temperature and pressure – is found only in the thick, ancient and stable parts of continental plates where regions of lithosphere (the rigid outermost shell of a rocky planet) known as cratons exist.

 

The diamonds are brought close to the earth’s surface by magma through deep volcanic eruptions. This magma cools into igneous rocks known as kimberlites and lamproites.

 

Kimberlites, which occur in the earth's crust in vertical structures known as kimberlite pipes, are the more important source of mined diamonds. This does not, however, mean that lamporites cannot yield significant volumes of diamonds. One of the best known lamporite mines is the Argyle mine in Western Australia, which was discovered in 1979 and which led to a reassessment of other lamporite occurrences worldwide.

 

Exploration

The first thing to understand about diamond exploration is that it is a long, drawn out process. Unlike the 1849 gold rush in California where gold was discovered at Sutter’s Mill in Sacramento and just a year later the area was being mined by thousands of hopeful fortune seekers, modern diamond exploration is a lengthy process that offers no guarantees. For example, although the pipe at the Diavik mine in Canada was discovered in 1994, it was not until 2003 that the mine finally opened and began producing goods.

 

Not only do many, many scientific tests have to be carried out, but with an increasing concern for the environment (from both mining companies and governments), miners have to satisfy regulatory requirements at every level that – as far as possible – they are minimizing the damage to and affect on the local environment and habitat.

 

Stage One: Identifying Potential Targets

So, you want to be a diamond miner? The first thing that has to be done is to identify an area that has the potential to contain diamonds. Don’t forget, it has to be within a stable cratonic environment, as this is where diamonds are likely to be found – if you are lucky.

 

Stage Two: Checking The Target

Once you have found a likely spot, you have to begin testing the kimberlite to see if your predictions were spot on and there are diamonds to be found, or if you have to move onto a different area. This is done through a process known as “caustic fusion,” which is every bit as scientific as it sounds. Essentially, a drilling sample is “digested” by caustic soda which literally “eats” everything in the sample but leaves behind any microdiamonds.

 

Once the diamonds are – hopefully – extracted, they are sorted through sieves to determine not only how many diamonds are present, but also their size. If there are enough diamonds, and if their size is considered large enough, the process moves onto the next stage.

 

Stage Three: Testing For Larger Diamonds

At this stage, mini-bulk sampling takes place. What this essentially means is that a sample of kimberlite will be tested to see how many diamonds it contains. Diamond grades are generally expressed using the measurement of carats per ton (cpt) or carats per hundred tons (cpht) (One metric carat is equivalent to 0.2 grams in weight.). It is this figure that is used to determine if a deposit can be taken forward as a productive mine. At the exploration stage, the amount of kimberlite sampled could be just a few tens of tons, a figure that could increase to somewhere around several thousand tons if the development reaches the feasibility study stage.

 

Stage Four: Testing For Grade and Value

Once it seems clear that a good number of diamonds are present in a particular area, it’s time to really test the kimberlite to make sure diamonds are spread out throughout and not just grouped in one section. At this stage, somewhere in the region of 100 tons of material is processed to verify grade and stone value.

 

Stage Five: Testing For Economic Viability

Congratulations! The kimberlite is full of diamonds, they seem to be large and they seem to be good quality. But hold on, there’s still a way to go yet. At this point, the project has to undergo a bunch of studies, from feasibility, environmental and socio-economic. According to exploration company Stornoway, the feasibility studies answer the following questions: “What is the best approach to develop the deposit? What is the capital cost going to be? What will the operating costs be? What is the optimum scale of operation? What are the likely revenues from the operation? What are the overall economic returns to be expected from the investment?”

 

Stage Six: Developing The Mine

The mine has passed all the tests, now all that’s left is the licensing, permits, design and construction of the operation. Let the mining commence!

 

Alluvial Mining

With all this high-tech exploration, testing and exploration, it is all too easy to think that diamond mining only consists of noisy, dirty work, full of heavy machinery and complicated equipment.

 

This type of mining accounts for about 76 percent of the world’s diamond mining industry, but another sort of mining also exists – alluvial mining, which makes up the balance.

 

Alluvial diamonds are those that have been unearthed from their primary source (Kimberlite) by millions of years of natural erosion and have found their way to river beds, the ocean floor or a shoreline.

 

While around 10 percent of diamonds are acquired by formal alluvial digging, a larger portion, as much as 14 percent of diamonds, are sourced by informal alluvial (also known as artisanal) diamond diggers. These artisanal diggers use extremely basic equipment, often no more than sieves and pans, in their search for diamonds, which often takes place on land that has neither been licensed nor regulated for mining activities to take place.

 

In order to reach the diamonds, diggers must remove the sand from the river banks on which they work and then extract and wash the gravel that lies underneath in the hope that a diamond will literally be found lying in the rough.

 

This type of digging has led to conflict, particularly in Zimbabwe where alluvial miners in the Marange (Chiadzwa) diamond fields were attacked by government forces.

 

All told, it is estimated that 1 million plus people in Africa work in the informal mining sector. However, some calls have gone out for increased regulation by granting large companies the concessions for these alluvial mines.

 

Companies such as Rockwell Diamonds, Namakwa Diamond, Diamcor Mining Inc. and Gem Diamonds are involved in formal alluvial mining. Rockwell is currently focused on the mining and development of alluvial diamond deposits in the Northern Cape Province area of South Africa. Namakwa runs an alluvial operation in the Tshikapa Triangle in the Democratic Republic of Congo (DRC), Diamocor operates the Krone-Endora alluvial project in South Africa, which it purchased from De Beers Consolidated Mines, while Gem Diamonds operates alluvial projects in the DRC and the Central African Republic.