Mohs scale of mineral hardness finding the hardest material that the given material can scratch, or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5. "Scratching" a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye. Frequently, materials that are lower on the Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number. While these microscopic dislocations are permanent and sometimes detrimental to the harder material's structural
71 Harrington Street, The Rocks and working classes in residence in The Rocks between the 1890s and the mid 1970s. The place is important in demonstrating aesthetic characteristics and/or a high degree of creative or technical achievement in New South Wales. The retained section of the house has aesthetic significance as part of a strong visual precinct forming a characteristic Rocks townscape with the adjacent terraces and the Harbour Rocks Hotel on the other side of the street. The retained street section of the former house enhances the human scale of the streetscape and reinforces the historic character of The Rocks. The item meets this