> I didn't realise the hunt for the pipe had ended.

Well the hunt for the actual source pipe ended some time back, the thinking being that most if not all of it had been ground down and cast into the giant bank that was the mine .. but hunting for pipes in general never ends - it's an ongoing part of any and all magenetic surveys to flag the distinct peaks of an magnetically aligned Kimberlite pipe.

( ^^ left in for posterity, clearly at odds with your article :-) )

Now reading your article (thanks) I find my recollection of the geology to be at odds with the article .. I was under the foggy recollection that the mine was alluvial - of diamonds that had been broken away from a pipe and banked up in gravel .. the article talks as if it was directly mining an intact pipe .. nope, correction, mining the alluvial deposits from a named pipe ..

Okay - they mined part of the remaining pipe (the remainder wasn't "economically viable) and the gravel deposits downstream.

That makes sense .. I must have an old memory of a missing diamond pipe somewhere else.

And yes, most diamonds found would be industrial grade and not gem grade.

FWiW many diamond pipes are only good for 40 or fifty years if that - what tends to be lost in the details is that some areas of the world have a high number of diamond pipes in close proximity and some mines clean up a few at once or one after the other.

Thanks again for the article, skimmed for now, bookmarked for 'ron.