First, you measure the mass of the rocks. You can put them on a small scale, and typically you measure them in grams. This determines the weight, or mass of the rock.
Next, you measure the rock like you would measure a 3D shape. You measure its approximate length (centimeters [cm] may work best, depending on the size of the rock). Measure the length, width, and height. This determines the volume.
Density is how solid something is. If an object has a large volume, but small mass, it is NOT dense. if it has a small volume, and a lot of mass, it IS dense.
To calculate density, take the mass number, and divide it by the volume, as shown (mass/volume) or [tex] \frac{mass}{volume} [/tex]
To show how you determined density, just show your calculations for each process. The one with a larger density number is the more dense rock. Hope this helps, and hope I was the brainliest! :)