This section is from the book "The Engineer's And Mechanic's Encyclopaedia", by Luke Hebert. Also available from Amazon: Engineer's And Mechanic's Encyclopaedia.
A species of blue stone with a sharp grit, employed for sharpening knives and coarse instruments upon. It is abundant in Kent, at Newcastle, in Northumberland, and at Rowley, in Staffordshire.
© 2007-2021 StasoSphere.com