How does a diamond look in the process of forming?

also would the immature diamond have any value or could it be sold?How does a diamond look in the process of forming?At the beginning it would look almost like a piece of charcoal, as it would be pure carbon. It has to undergo an immense amount of pressure for a very long time to form an actual diamond. An immature diamond would have very little value, and would be next to impossible to sell.