Australian geologist EWEN TYLER played a significant role in the discovery of Australia’s three diamond mines. Here, he reveals how they were uncovered and the impediments for diamond exploration today.
It’s never been easy to find a diamond mine and the issues encountered during the discovery and establishment of Australia’s three diamond production centres at Argyle, Ellendale and Merlin prove just that.
After 20 years working in mining exploration in Africa and Europe, I was asked to return to Australia to search for diamonds for Tanganyika Holdings. Diamond was known to exist in every Australian state but only the Wellington Alluvials in NSW had any significant production.
I had studied geology at the University of Western Australia under Rex Prider.
From his researches, Prider postulated that strange rocks in the Fitzroy Valley, known as leucite lamproites, were very similar magmatically to the diamond-bearing pipes in South Africa.
In 1969, because of Prider’s research, I asked my Perth office to design and cost a search program in the Kimberley for kimberlite. As my funds were limited and joint ventures were becoming fashionable, I invited AO (an Australian subsidiary of London Tin Corporation), Belgian diamond company Sibeka, Jennings Mining (a company with previous Kimberley experience) and Northern Mining, of which I was a director, to come on board. Each would contribute $20,000 to meet the $100,000 budget, and so began the Kalumburu Joint Venture.
The search begins
Kimberlites are diamond-bearing ultramafic rocks that source in the earth’s mantle from depths greater than 150 km; they are effectively diamond-bearing volcanoes. Because of the low abundance of diamond even in a kimberlite, an economic deposit content may be as low as 1:100,000,000.
The explorer does not expect to find a diamond sticking out of a volcano as one might see a gold nugget in a quartz vein. Instead he looks for ‘indicator minerals’ that form at a similar depth to diamond but are more abundant. Usual indicators are pyrope garnet, picroilmenite, chrome diopside and chromite.
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