Explanation:
The terms heavy and light are commonly used in two different ways. We refer to weight when we say that an adult is heavier than a child. On the other hand, something else is alluded to when we say that rock is heavier than soil. A small rock would obviously weigh less than a roomful of soil, but rock is heavier in the sense that a rock of given size weighs more than the same-size sample of soil. What we are actually comparing is the mass per unit volume, that is, the density. In order to determine these densities, we might weigh a cubic centimeter of each sample. If the rock sample weighed 2.71 g and the soil 1.20 g, we could describe the density of the rock as 2.71 g cm–3 and that of the soil as 1.20 g cm–3. Even though sand is made of rock fragments, its density is less because the porosity of sand lowers its bulk density (as shown below). (Note that the negative exponent in the units cubic centimeters indicates a reciprocal. Thus 1 cm–3 = 1/cm3 and the units for our densities could be written as g/cm3, or g cm–3. In each case the units are read as grams per cubic centimeter, the per indicating division.) We often abbreviate "cm3" as "cc", and 1 cm3 = 1 mL exactly, by definition.
Table 1 : Density of Soils and Rocks
sand
1.52
sandy loam
1.44
loam
1.36
silt loam
1.28
clay loam
1.28
clay
1.20
amphibolite
2.79–3.14
dolomite
2.72–2.84
gneiss
2.59–2.84
limestone
1.55–2.75
marble
2.67–2.75
schist
2.73–3.19
shale
2.06–2.67
slate
2.72–2.84
pyrite
5.0
gold
