Make Gravel Useful (able to get nuggets and gems)

After mining for a short while I found my inventory full of gravel. I had a quick thought of a sieve or pan that could process the gravel with a chance to obtain certain items like,

Flint - common
Iron Nuggets - uncommon
Gold Nuggets - rare
Diamonds - Very rare
Emeralds - Extremely rare

The sieve could be hand work, while a pan requires running water but is automated like a furnace or something like that.