Ann: Mines and Money London Presentation, page-39

Re Sharpness of diamonds

Chief executive officer Stephen Wetherall believed the company was on the cusp of discovering the original source of the stones, which could make it a takeover target for some of the largest diamond miners in the world.
He said the number and condition of the diamonds collected in the area over the past 12 months suggested the company was close to the major deposit.
He explained the size, shape, and roughness of the large stones found recently suggested they had not travelled far from their original seam, while stones found further from their source generally had more polished surfaces and a rounded shape.

http://www.abc.net.au/news/2016-09-21/perth-companys-104-carat-diamond-find/7865046