* Density: This refers to the mass of the rock per unit volume. It's a measure of how tightly packed the material is. You could say "This rock is dense".
* Weight: This refers to the force of gravity acting on the rock's mass. You could say "This rock is heavy".
It's important to differentiate between these two terms:
* Density is a property of the material itself, independent of gravity.
* Weight is a force that depends on the mass of the rock and the gravitational field it's in.
You could also use the term specific gravity which is the ratio of the density of the rock to the density of water. This tells you how much heavier the rock is compared to the same volume of water.
Ultimately, the best way to describe the heaviness or density of a rock depends on the context and what you want to convey.
