What is the hardest mineral in nature?
The natural minerals we know are the rocky and metallic substances of the Earth’s crust. These upper layers of the solid Earth reach down only 10 to 40 miles, and no one has been down to Explore what materials lie beneath them. Down in the depths of our solid planet there may or may not be minerals much harder than those we know on the surface. Every rock hound knows that hardness is one of the tests used to identify a new specimen from the crusty ground. The classes of mineral hardness run from 1 to 10, with degrees of difference in each class. Sulphur has a hardness of exactly 2. Borax, with a hardness of 1.7, is between classes 1 and 2, while glassy topaz, with a hardness rating of 3.5, is midway between classes 3 and 4. The way to test the hardness of a new rock sample is to scratch it. A lump of calcite in class 3 can be used to scratch gypsum of class 2 and talc of class 1. A mineral from a harder class can scratch all the minerals in the softer classes, but the softer minerals c
