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Stone found on the Thames foreshore

Tim Matthews wants to know what this is.

He writes:

It's about 3" long, 3/4" diameter, flat at one end (possibly broken off) rounded at the other, made out of stone or some mineral and has a rifled hole going through the middle. It's the purpose of the rifled hole that's puzzling me which must have taken a fair effort to drill - I'm wondering if it's a worn-down grinding stone, but surely a simpler square hole would suffice?


Having thought about it overnight I am wondering if it is a ”Mounted point” ie whether it is a synthetic grinding wheel which was made by moulding powder round a basically circular shaft to fit into either a chuck on a flexible shaft or the tail-stock of a lathe. The fancy interior shaping would make it much more securely attached and, since the grinding material was applied as a powder round a steel mandrel and then fused/fired to solidify it there would be no problem in drilling the hole.

I have attached a scan from a 1945 pamphlet issued by The Carborundum Company to give you an idea of what was then available but I don’t have any clearly dated earlier publications, although such synthetic stones were available from late Victorian times. As to what size it was originally, it was probably much the same as now and what has happened is that it has separated from its mandrel somehow.

I don’t know if you have any access to analytical facilities at all but it might be worth while seeing exactly what the material is – if it is silicon carbide or another synthetic material then that solves the problem.

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