the hardness of minerals is measured on the mohs scale.
the hardness of minerals is measured on the mohs scale.
the hardness of minerals is measured on the ____ scale?
mohs scale
the mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly. the samples of matter used by mohs are all different minerals. minerals are chemically pure solids found in nature. rocks are made up of one or more minerals. as the hardest known naturally occurring substance when the scale was designed, diamonds are at the top of the scale. the hardness of a material is measured against the scale by 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 integrity, they are not considered "scratches" for the determination of a mohs scale number.
mohs scale of mineral hardness
the hardness of a material can be measured in many ways. the knoop hardness test, a method of microindention hardness, is the most reproducible for dense ceramics. the vickers hardness test and superficial rockwell scales (e.g., 45n) can also be used, but tend to cause more surface damage than knoop. the brinell test is suitable for ductile metals, but not ceramics. in the knoop test, a diamond indenter in the shape of an elongated pyramid is forced into a polished (but not etched) surface under a predetermined load, typically 500 or 1000 g. the load is held for some amount of time, say 10 s, and the indenter is retracted. the indention long diagonal ("d", μm, in fig. 4) is measured under a microscope, and the knoop hardness (hk) is calculated from the load (p, g) and the square of the diagonal length in the equations below. the constants account for the projected area of the indenter and unit conversion factors. most oxide ceramics have a knoop hardness in the range of 1000–1500 kg/mm (10 – 15 gpa), and many carbides are over 2000 (20 gpa). the method is specified in astm c849, c1326 & e384. microindention hardness is also called microindentation hardness or simply microhardness. the hardness of very small particles and thin films of ceramics, on the order of 100 nm, can be measured by nanoindentation methods that use a berkovich indenter.
ceramography