Minecraft wiki entry for Gravel, associated text: Gravel can be broken using any tool, but a shovel is the quickest. When broken, it has a 10% chance of dropping flint instead of the gravel itself. The flint received can be controlled with enchantments. Silk Touch removes the chance of dropping flint. Fortune increases the chance to 14% at the level I, 25% at level II, and 100%[needs testing] at level III.[1][2]