Pumice.
rocks, metals ect.
The extrusive volcanic rock pumice can float on water. Other extrusive volcanic rocks are not so lucky.
Because rocks are more dense than water
Rocks are generally denser than water, so they sink instead of floating. The buoyant force acting on an object in water is not sufficient to counterbalance the weight of most rocks, causing them to sink. Additionally, rocks are not porous enough to trap enough air to make them float.
They play with rocks that float around in the water
Any object that is less dense than water will float.
Well rocks don't float because they are a solid with no air.
Items with a higher density than water do not float, such as rocks, metals, and most plastics. Additionally, items that are porous and absorb water, like paper or cloth, can become saturated and sink.
Yes, the data dates back to the Greek mathematician, Archimedes. He discovered that when the mass of an object placed on the water is less than the mass of the water it displaces that object will float. Supertankers cover much area with their mass (thus displacing much water), while rocks generally (with the exception, for example, of pumice) do not.
Pumice stones will, these are low density rocks formed by volcanoes
too dense to float
Pumice rocks have been known to float across oceans.