He called it the Mohs hardness scale . Anyway, The Mohs hardness scale rates ten minerals from diamond, the hardest mineral, to talc, a very soft mineral. 10 Things get harder as you increase the number. So, quartz is harder than calcite. Also, quartz will scratch calcite, but calcite won't scratch quartz.
Calcite is harder than gypsum, however, because it has a higher number.
The next physical property we use to identify and classify minerals is called cleavage . Where and how minerals split, or cleave, depends on the strength and arrangement of the bonds in their crystal structure. The next physical property of minerals is luster . Luster refers to the way that minerals reflect light. A mineral with metallic luster looks like a metal when light reflects off it.