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.
Lilyvale, The Rocks majority of external render was removed and the brick walls painted. As at 30 March 2011, "Lilyvale" and site 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. "Lilyvale" Cottage is a very fine and rare example of Colonial Regency freestanding domestic architecture in the city centre. It is in good condition, having been conserved in 1987 by SCRA, and retains much of its early form and materials. The cottage