Gravel

Gravel is a block that falls when nothing holds it up, and the only source of flint.

Obtaining

Breaking gravel drops flint one time in ten, and gravel otherwise, whatever breaks it. A shovel breaks it fastest.

Gravel forms veins in stone, as an ore does: 10 per chunk, of size 32, from y=0 to y=127.

Between y=60 and y=65, rare stretches of the surface have gravel in place of the biome's filler, and water or air in place of its top block.

In the Nether, gravel tops about half of columns whose surface lies between y=60 and y=65, except where soul sand takes them.

Gravel can be duplicated with timed piston movements.

Gravel falls when the block below it is air, water, lava or fire.