What Makes a Rock Hard or Soft?

Kaya lives in Westlin, Oregon and is 10 years old. Why can you draw with some rocks? That has to do with the hardness of the minerals that are in the rock. If a rock has all of these three properties, then you can draw with it. For example, say a tauk, maybe calcite. What are the minerals are slippery and smooth so that when you pull it on a surface, it can leave a mark. And also, whether the mineral has a color that you can distinguish from what you're drawing on. Can you imagine you can go from graphite and become as hard as diamond?