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.
121 George Street, The Rocks and has been continuously occupied for commercial and retail purposes since construction in 1880. The building's scale and alignment to the street is typical of that found along the west side of George street and lining the harbourside as part of the business precinct of The Rocks. The building is part of the rich fabric of The Rocks which is highly regarded by residents, Sydney people and visitors and acknowledged by the Australian Heritage Commission and the National Trust as part of The Rocks Urban Conservation Area. The building at 121 George street is expressive of the close weaving of