The mine is an open pit operation based upon the 146 hectare Mwadui kimberlite pipe, which is the world’s largest economic kimberlite to have seen continuous mining.

Despite having been in operation since 1940, the pit is only 95 metres at its deepest point due to the large size of the deposit. The low grade of the deposit is countered by the high value of its diamonds and lends itself well to high volume, bulk mining methods.

Opencast operation at 90 metres (deepest point).
Williamson is Petra’s first open pit mine and is the most important diamond operation in Tanzania. At 146 hectares, the Mwadui kimberlite (on which the mine is based) is the largest pipe ever to be mined continuously, having been operated as an open pit mine.

A low capital cost solution was required to increase diamond production that would not significantly increase the current operating costs. A conventional diamond treatment plant was considered to retreat the old DMS tailings but proved too costly. Williamson were aware that Debtech and Gekko Systems had been successfully performing trials to remove shell from marine gravels using the IPJ, and saw an opportunity to also test the application of the IPJ on their old DMS kimberlite tailings.