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.
105 George Street, The Rocks at 105 George Street, are of State heritage significance for their historical and scientific cultural values. The site and building are also of State heritage significance for their contribution to The Rocks area which is of State Heritage significance in its own right. 105 George Street is a reconstructed, typical example of a simple 19th century shop and residence. The building has been used for commercial purposes for more than 150 years. The building makes an important contribution to the surrounding 19th century commercial precinct and contributes to the character of the surrounding area of The Rocks. 105 George Street,