Restores maximum stats of a tree when dropped on to it
Restores maximum stats of a rock when dropped on to it
Reduces small amount of time on total construction time when dropped on building being constructed
Dropping it on a Tribe member reduces the time needed to reach the next level by 1 hour.
Gives a fair amount of science points when dropped on the science station (depends on the level of tech)
Picking up fallen Stardust allows you to gain XP. Stardust can be used on many things on your island, including tribespeople, construction projects, and mysterious objects. It is also a common ingredient for crafting.