Given that progression (deeper underground, more precious ores, accumulated money, presumably also improved equipment, maybe other elements) seems the focus of the game, it should be a good starting point for designing ore distribution. Design objectives for the digging can be written down and random distribution of ore adjusted to match them.

• How long should it take to dig everything in a level or to dig enough to figure out it's a poor one?
• If encumbrance, weight, tool wear etc. matter, what range of dug ore per level is neither too easy nor too difficult to handle?
• How much should a level's worth of ore be worth? What is money useful for?
• How much should runs of bad levels limited? What are the limits of the player's patience and resources?
• How much should runs of good levels limited? CAn the rest of the game become too easy?

There are several mostly independent options to adjust the progression:

• you can disperse more or less widely the same ore within a level to require more or less mining work to get it
• you can place the same ore in more or less levels to make the player dive faster or slower (assuming something important depends on current depth)
• you can estimate the net worth of a level and force the player to spend accordingly
• you can choose different substances for the same value and/or amount of ore (e.g. to feature them all, to leverage special purposes or properties, because they are distributed differently…)