There is many items in Mining Quest. Each item has a rarity. Here is a list of rarities.

Rarity List

Rarity About
Basic/White A decent kind of item. They include dirt, stone and ruby. Every kind of coin is a white rarity and your pickaxe/drill (at any level) is this rarity..
Good/Blue A good item. Sapphire, emerald, granite and more. Sometimes drops off enemies like Plasm potions are this rarity.
Great/Orange A great item. Amethyst, invincibility potions and Topaz are this rarity. Also hard-rock is this rarity.
Epic/Green Items this rarity are epic. They include diamond, bedrock and normal Clay.
Awesome/Yellow Awesome items are this rarity. Musgravite, blue clay and the Cloud Rod are this rarity. More items could be coming to this tier soon.
Legendary/Purple These items are mythical. They are Corestone, golden Clay, Magmacore and every kind of pot is this rarity.
Special/Pink These items are given to you by NPCs.
Secret/Grey These items are secret items that are unlocked by doing secret things, like after defeating Ttam, if you check the vacant house's pots you will get an item that is this rarity, the Crimson Flowers.