Of all the objects in a normal outdoor environment, rocks are generally the densest. However, not all rocks are the same density. Granite is an igneous rock, which is composed of grains of quartz, feldspar and plagioclase granite forms . The amount of these components can vary, and the rock can even contain cavities, so the density of granite ranges from about 2.5 to 2.8 grams per cubic centimetre (g/cm^3).
The lighter granite rocks can be less dense than some sedimentary rocks, which are different from granite in that they form over time through sediments sticking together, unlike granite, which is formed through volcanic energy. The densest sandstone can reach 2.6 g/cm^3 and shale can be up to 2.7 g/cm^3. Limestone, as it spans the same density range as granite, has some forms of rock that are denser than some forms of granite.
In the igneous rock grouping, granite is less dense than basalt rocks, which are dark rocks with very small crystals that are reflective and glass-like. The range of densities for basalt runs from 2.7 g/cm^3 up to 3.1 g/cm^3.
The metamorphic rocks are the densest of all the major types of rocks. This is because they form from other types of rocks and minerals through high pressure, so the rocks or minerals get squashed together and therefore become more dense. Examples of metamorphic rocks include marble, slate, gneiss, schist and quartzite. Diamonds, which are squashed graphite, are also more dense than granite, at 3.52 g/cm^3.
Metals are dense by nature, and most are much denser than granite, although some, such as magnesium, can be less dense. For example, iron has a value of 7.8 g/cm^3 and copper at least 8.3 g/cm^3. The precious metal gold has a density of 19.3 g.cm^3, which is almost twice as much as lead, which has a value of 11.4 g/cm^3. Platinum is even denser at 21.3 g/cm^3. The radioactive element uranium has a density of 18.7 g/cm^3. Even though mercury is a liquid at room temperature, it too is denser than granite at a value of 13.6 g/cm^3. Despite the association of aluminium with items such as light and floaty tinfoil, aluminium actually has a density of 2.7 g/cm^3, which means it is denser than some granites.