Sand

"Sand spawns naturally in four-block-deep layers in various parts of most biomes of the Overworld. You'll find it everywhere from forests, to plains, to tundra and swamps. In Mesa biomes, you'll find a variant of sand that's red and acts exactly like regular sand except that you can't use it to make concrete. Actually, that sounds like a bug. Maybe we should fix that."

- Duncan Geere

Sand is a block affected by gravity.

Red sand is a variation of sand, the only differences being its color and that it cannot be used to craft concrete powder.

Obtaining
Sand can be broken without tools, but a shovel is the fastest.

Natural generation
Sand generates naturally in many biomes of the Overworld, notably deserts, beaches, and rivers, generally in four-block-deep layers supported by stone and sandstone.

Red sand generates naturally in mesa biomes and variants.

Sand can spawn floating in the air. The floating cluster of sand will fall when one of the sand blocks receives an update (when a block is placed near it or when a block near it is broken).

Usage
Sand, if there is no block below it, will fall until it lands on the next available block. When sand is being affected by gravity and falling, it exhibits a smooth falling animation.

If falling sand lands on a mob or the player and covers their head, it will suffocate them until they destroy the block, move out, or die. If falling sand lands in the space occupied by a non-solid block, (such as torches, slabs, rails, or redstone), it will drop and turn into a sand item. If it falls onto a cobweb it will slowly fall until it has gone through it completely, or until it touches the ground, at which point it will turn into a resource block.

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

If a sand entity falls on a fence post, it does not turn into a solid block. Instead, it stays as an entity on top of that fence post.

Construction
Sand can be used in the construction of airlocks and the creation of mob suffocation traps. Being affected by gravity, it can be quickly and easily removed from ground level.

Farms
Sand and red sand can be used for farming cactus and sugar canes.

Data values
Sand has the ID name  and is further defined by its block data. Sand also has a block state which is expected to replace the functionality of block data in a future version.

Trivia

 * If a block of sand has snow on it and is made to fall, the snow is destroyed and will not drop snowballs.
 * Because falling sand is considered an entity it can be launched in a TNT cannon, similar to an ignited piece of TNT.
 * Sand will fall at the same rate when submerged in water as it will when in air.
 * If a player is standing on a stack of sand or gravel, and the stack falls on a non-solid block, the player will fall fast enough to take damage or even die.
 * Sand will fall through torches without breaking if there is air below the torch.
 * Sand and gravel take about 0.45 seconds to fall one meter.
 * The sand texture will actually be rotated if a block of sand turns into a FallingSand entity, similar to ignited TNT blocks. This is not the case with gravel.
 * Because  is an entity, blocks of sand without supports may disappear for a split second and a   entity is summoned. This is also the case when it's landing, but the entity (not the block) disappears instead before a block is placed.