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.
Our Lady of the Rocks long journey, and eventually, she became blind. She used golden and silver fibres but what makes this tapestry so famous is the fact that she also embroidered her own hair in it. Our Lady of the Rocks Our Lady of the Rocks (, ) is one of the two islets off the coast of Perast in Bay of Kotor, Montenegro (the other being Sveti Đorđe Island). It is an artificial island created by bulwark of rocks and by sinking old and seized ships loaded with rocks. The Roman Catholic Church of Our Lady of the Rocks () is the largest