One identifying characteristic of minerals is their relative hardness, which can be determined by scratching one mineral with another. In this type of test, a harder mineral can scratch a softer one, but a softer mineral is unable to scratch the harder one. The Mohs' hardness scale is used to rank minerals according to hardness. Ten minerals are listed in this scale, ranging from talc with a hardness of 1 to diamond with a hardness of 10. On this scale, quartz (number 7) is harder than feldspar (number 6) and is therefore able to scratch it; however, feldspar is unable to make a mark on quartz.