Azurite

Azurite is an ore added in Alpha 3. It mimics Azure Mines' Opal, with it having a unique look and only spawning in the first few layers.

Trivia

 * Even though it seems like Azurite is a fake gemstone with an attempt to draw in more players, that isn't the case. Real-life azurite looks really similar to in-game azurite.
 * However, it is possible that the creator added this in an attempt to duplicate Opal.
 * Another thing that makes this unlikely is the fact that Bismuth Mines has it's own, unique version of Opal.