Scratch hardness Scratch hardness Scratch hardness tests are used to determine the hardness of a material to scratches and abrasion. The earliest test was developed by mineralogist Friedrich Mohs in 1820 (see Mohs scale). It is based on relative scratch hardness, with talc assigned a value of 1 and diamond assigned a value of 10. Mohs' scale had two limitations; it was not linear, and most modern abrasives fall between 9 and 10. Raymond R. Ridgway, a research engineer at the Norton Company, modified the Mohs scale by giving garnet a hardness of 10 and diamond a hardness of 15. Charles E.
93 George Street, The Rocks development of The Rocks. The site has scientific significance for the archaeological potential to reveal evidence of road surfaces and earlier buildings on the site. The building is socially significant for its long history, and for its contribution to The Rocks area, Australia's premier heritage precinct. Shop, Zia Pina Pizzeria was listed on the New South Wales State Heritage Register on 10 May 2002 having satisfied the following criteria. The place is important in demonstrating the course, or pattern, of cultural or natural history in New South Wales. The site of 91 and 93 George Street is historically significant as