Stardew Valley Wiki

Mining is the act of digging in the Mine in Stardew Valley. This will help the player gain mineral-based Resources which can be smelted into bars, sold, donated, or used in further crafting. When mining, the player will also have to fend off any number of enemies using the combat skill.

The mines themselves consist of 120 levels total; these are randomly generated as you progress. You can "save" your progress in a sense every 5 levels; that is if you get to level 5 you can always return there if you exit the mine by using the elevator. You progress through the mines by breaking rocks or fighting enemies, with a random chance of a ladder to a lower level spawning. However, you can lose access to these levels by getting your health reduced to 0, with the game-logic saying you "forgot" those levels. You can additionally lose items by having your health depleted completely, and as such it should be avoided at all costs.  There are rewards every 10 levels. The most notable levels being the 100th awarding a "stardrop" which increases your maximum energy permanently and the 120th level awarding you the skeleton key.

The players' ability to mine is measured as a skill; you will learn new crafting recipes relevant to mining, and additionally have a Level 5 special skill choice of either extra ore or extra mineral chance.

The primary ores are copper, iron, and gold and can be smelted using a Furnace into their respective bars by using x5 ore and x1 charcoal.

Tilling cave dirt: If you use your hoe on the dirt patches in the mines, you have a chance to find different loot. It seems like a semi-reliable source for clay.

Items found on level~5: cave carrot, geode, omni geode, clay, rusty spoon (artifact), stone,