Flint

Flint is an expendable object found by digging gravel. When destroying gravel blocks, there is a 10% chance that a single unit of flint will drop instead of receiving the gravel block back. It is possible to farm flint by erecting high stacks of gravel and then power-mining it down. Note however that this is a one-way process: there is no way of turning flint back into gravel.

Gravel, along with other blocks that are affected by gravity, can be harvested quickly by placing a torch under a tall stack of it, then breaking the gravel immediately above it. The gravel blocks will instantly break when they hit the torch, causing the entire stack to be mined quickly. Using this tactic, however, will not yield flint; you must manually mine gravel with a tool or your hands if you wish to increase your supply.

Trivia

 * After the 1.3 update, finding flint is more common.

Feuerstein Silex Kovakő Kiezel Krzemień Кремень