A Stone (also called a Rock) is a type of Obstacle in Surviv.io. It is gray with a smaller gray circle inside, with a black outline.
The Stone is a breakable object, however, it drops no loot. The only exception is the Rock/Stone Cache, which drops an AK-47, an Initiative skin and some additional loot. Look for points under the rock in the cardinal directions.
A ridiculous number of stones spawn around the map, and you are almost guaranteed to run into one; they seem as common a trees.
Stones take 11 punches to break, while Trees only take 8 and Crates take 4.
Stones have 250 Health.
Stones can be lifesavers while you are being shot at with a weak gun. Hide behind it and keep the rock between you and the opponent.
However, it is not recommended that you shield yourself with a stone when someone with an M249. Being am LMG, it will decimate the stone in seconds.
Also watch out for Sniper Rifles, as most can 2 or one-shot a rock.
Grenades are also dangerous, as they can blow up both the rock, and you.
Durning the "Snow-covered Island" event, rocks have snow on their upper-left part. This seems to have no in-game effect.