Minecraft wiki entry for Falling_blocks, associated text: Extra data can be inserted in the NBT (Named Binary Tag) to modify the time in seconds the block remains in the air. This NBT is Time, which stands for the time (in ticks) for how long the falling_block has existed. If 0, the entity despawns, if 1 or greater, will continue ticking up, until it reaches its maximum lifetime of 600 ticks, or 30 seconds, at which point it turns into a dropped item. The least time value you can give a falling_block is -2147483648 (the lowest number that can be represented as a 32-bit integer). Below this value, the block will immediately despawn. It will also turn into an item if it has existed for more than 100 ticks (5 seconds) and is outside the build limit (above y=320 or below y=-63). Adding a value of time for the block will cause the block to assume a physical form when coming in contact with the ground, just like a normal sand block falling downwards. Ensure that the different data values are separated by commas: