Digging and Sifting Through Decks -- Already Been Done??

I'm not familiar with any game that allows players to sift or dig through piles on the board, however there are a number of games that allow players to search through the discard pile(s) and take the card they want. Might this be similar to what you're describing?

It may be interesting to develop a real-time digging mechanic for a game such as the one you're designing...Any thoughts on that?

EDIT: and there's also the idea of "cycling" through a deck or pile of cards. In this method, players take a pile and go through it one card at a time, collecting one or more cards as they go. The thing that makes this particular is the notion that players must go from one card to another in sequence, not picking and choosing which card they encounter.

Why might this be an important distinction? Take for example a mining game. Maybe a player wants to look for three gold ore cards. However, if at any time two cave-in cards are discovered, then the player loses their chance to continue cycling. It's a deck-based "press your luck" mechanic, in sum. The player must choose to continue on their current turn and risk what they've already collected, or they can play it safe and stop digging until next turn - when cards will have been shuffled or re-organized in some way.

I've seen a few mining games, none specifically like this. The one thing I would caution you about is that most games I've played that allow players to look through decks of cards suffer from some serious down-time issues. If you're going to allow someone to "survey" and look through decks, would it be possible to do that when it is NOT their turn, so as to speed things along?

Not only would it mean you don't take a long time on your turn looking through all of the cards in a deck, it would also mean that players have an incentive to play their actual turns quickly so that their opponents don't have a lot of time to survey.