Diamonds form in cometary impacts, comets are made from frozen carbon dioxide, under the tremendous heat and pressure of impact with the Earth's surface, the carbon turns to diamond.
The diamond pipes or clusters of pipes at diamond bearing locations attest to this, as do alluvial diamonds in stream sediments associated with impact fields, ie basins which formed during an ancient cometary impact. The Tweed Valley in far Eastern Australia is one such, the diamonds that turn up there the highest quality in Australia.
Similarly satellite photography has identified large impact basins in Western Australia, including a system of interlocking impact formations, visible on Google Earth, and on nightly TV Weather Maps of Australia’s mainland. Chart the locations of highly productive pipes and associated alluvial deposits at the rim of large impact basins.
Picture shots of drops falling into milk for instance, a crown like structure will appear, the points on the crown corresponds to the vents formed during impact that carries impacted material, and pieces of the comet, diamonds, to the surface. Typically a diamondiferous crater will have a central peak associated with the impact, see Mount Warning in the Tweed Valley, however the diamondiferous pipes are at the boundaries of the crater.
Obtain a GPS and go to the locations you have pinpointed from satellite photos, use an ultra violet light source to find which pebbles and pieces of gravel fluoresce in the UV, then find which stones will leave a scratch mark on glass. The ones that do are the diamonds, I have done this plenty of times and located some great stones from a hitherto unmapped source on Kangaroo Island, off the coast of South Australia.
Notwithstanding the enormity of wrongs that indigenous people suffer when industrial mining takes place on their homelands, this method is virtually fail safe, no more than hand shovels should be used. It was the method endorsed by the responsible government of Sierra Leone, prior to the warlords entering the industry.
Word is that at the diamond mines in South Africa the diamonds are getting bigger the deeper the miners dig, tales of boulder sized objects arise, where miners gather to drink and talk. When they get to the nucleus of the comet, maybe thousand ton diamonds will be found.