I feel my writers itch flaring up. I come from a line of writers and journalists. I feel this is going to be a long story. Gerhard Louwrens and I have just spent a fascinating morning with Peter Ringdahl. He explained in great depth and clarity the history and technology of synthetic diamond manufacture, illustrated with samples. His samples of synthetic diamonds look really stunning under his microscope. Not high purity, but each one with every crystal face perfectly formed.
But this story is not about the diamonds, it is the story about my involvement with pyrophyllite, a natural mineral without which synthetic diamonds cannot be manufactured. I have to leave out a lot of it for political reasons. One of my first involvements with pyrophyllite was with a synthetic diamond manufacturer. They milled the pyrophyllite, screened out the desired size fraction and threw the fine powder away in 110 litre drums. At the time, Keramicalia was a minerals by-product trading operation. (I was under a restraint of trade from my former refractories employer.) I offered them a better deal: I would dispose of it at no charge, but no only that; I would supply the drums at my own cost. They said they would think about it. After 2 weeks they decided they would rather carry on throwing it away at their own expense.
I was approached by a consulting geologist offering me pyrophyllite from the Wonderstone deposit in Ottosdal. I collected samples and found that the variation was too erratic. One end of a large rock would yield a perfect fired sample and a piece taken from the other end would disintegrate on firing. Pyrophyllite is a phyllosilicate, related to clays, with a texture and mechanical properties similar talc. Talc, also called steatite, is the soapstone from which ornaments are made in Zimbabwe and Swaziland. The Ottosdal pyrophyllite is grey to black in colour, and if you like sculpture, there are some enormous and intricate and almost unbelievable examples at Assore’s head office in Fricker street. Assore owns Wonderstone, the company mining the largest of the Ottosdal pyrophyllite deposits. The name Wonderstone was given to the Ottosdal pyrophyllite way back. I have a geological survey report on the deposit issued in 1937. (It cost 6 pence.) The deposit was then a mountain, now the mine is below ground. Wonderstone was machined on lathes etc. into intricate parts and then fired into hard ceramic components. Today most of it is milled fine, calcined, bonded with sodium silicate, pressed into shape and then fired.
At a foundries exhibition in Dusseldorf I saw a remarkable refractory brick. It was absolutely solid and smooth, looked almost like plastic. Sang-yu refractories invited me to visit their plant in China, and I did so some years later while on a pot shopping with Adriaan Turgel.