What does "from the rough" mean? [closed]

Diamonds found in jewellery ('jewelry' US) are cut, polished, shaped, etc, from 'rough diamonds' found in the ground. A finished stone is said to have been created 'from the rough'. It is not quite idiomatic to say that finished diamonds are 'dug out' from the rough, which makes me think that the sample text was prepared either by a non-native speaker, or a native speaker unfamiliar with diamond mining and gem terminology.

Pricing diamonds from the rough