Here's a breakdown of what this means:

* Naturally occurring: They are found in nature, not created in a lab.

* Solid substances: They have a fixed shape and volume at room temperature.

* Definite chemical composition: They are made up of specific elements in a fixed ratio. For example, diamonds are made of pure carbon.

* Crystalline structure: Their atoms are arranged in a highly ordered, repeating pattern. This pattern gives diamonds their unique hardness and sparkle.

So, while diamonds are special for their hardness and beauty, they share these fundamental characteristics with all minerals.