The density of a substance can be an important physical property to know. However, the density of a specific type of rock may not be a single number because rock composition varies with mineral content.
Quartz diorite is an intrusive igneous rock, meaning it was originally molten material that solidified underground. This rock is a mixture of the minerals feldspar, pyroxene, hornblende and quartz, which exist in varying proportions. The amount of quartz in a quartz diorite rock, for example, can vary from 5 percent to 20 percent.
Since the composition of each quartz diorite sample varies depending on the rock’s mixture of minerals, the density can vary also. The density range for quartz diorite is 2.74 to 2.77 g/cm3 with an average density of 2.75 g/cm3, according to Peter K. Harvey of the Geological Society of London.
Quartz diorite has a relatively high density. For comparison purposes, water has a density of 1.0 g/cm3. Granite rocks have a density range of 2.60 to 2.64 g/cm3.