Gravel

"Gravel has been a part of Minecraft since May 2009, when it was added to the game alongside other basics like sand, coal, and trees. Unlike those blocks, however, it's always been largely decorative - spawning in pockets underground that really get in the way when you're digging a tunnel, or in small quantities on beaches and near pools of water."

- Duncan Geere

Gravel is a block that is affected by gravity.

Natural generation
In the Nether, gravel generates naturally in large veins between Y=63 and Y=65 in one-block-deep layers. It often generates without blocks below it, in which case it falls when updated.

Gravel is also found on beaches, near small pools of water, river, in gravelly mountains biomes covering most surface and underwater covering bottom of normal, cold, frozen ocean biomes, and deep variants.

Gravel also generate as part of cold underwater ruins.

Mineral veins
Gravel can generate in the Overworld in the form of mineral veins. Gravel attempts to generate 8 times per chunk in veins of size 33, from altitudes 0 to 256, in all biomes.

Obtaining
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 level I, 25% at level II, and 100% at level III.

If gravel falls onto a non-full block, it drops as an item and will not drop flint.

Usage
A gravel block falls until it lands on the next available block below it. It exhibits a smooth falling animation.

When gravel falls on a player or mob, it can engulf the head, resulting in suffocation inside gravel until destroying the block, moving out of it, or dying. If falling gravel lands in the space occupied by a non-solid block, (such as torches, slabs, rails, or redstone dust) or soul sand, it breaks and turn into a gravel item. If it falls onto a cobweb, falls slowly until it passes completely through, or until it touches the ground, at which point it drops and becomes a gravel item.

Gravel can be placed on a non-solid block without falling.

Trading
Novice-level fletcher villagers have a 50% or $2/3$ chance to buy 10 gravel and one emerald for 10 flint as part of their trade.

Trivia

 * Explosions launch falling gravel.
 * If a player stands on a stack of sand or gravel, and the stack falls onto a non-solid block, the player falls fast enough to take damage or even die.
 * Gravel often falls into caves, making a mock dead end. If a player encounters a gravel dead-end while mining, removing the gravel may reveal additional passageways.