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.
123-125 George Street, The Rocks Free Classical style, executed to give a sense of decorum to what would otherwise have been simple commercial / residential structures. The buildings have streetscape value as two buildings in a group of three that were designed to appear as one property. The buildings' scale and alignment to the street are typical of that found along the business precinct of George Street in The Rocks area. The street façades have remained relatively intact since they were constructed in 1882. The place has a strong or special association with a particular community or cultural group in New South Wales for social,