Science, Maths & Technology

### Become an OU student

Minerals and the crystalline state

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

# 3.5 Density

Density is a measure of how heavy an object is for a given volume. You can get a general idea of the relative densities of different minerals just by picking them up: a piece of galena (PbS) feels heavier than a piece of quartz (SiO2) of the same size.

The density of a mineral depends on its chemical composition, the type of bonding and its crystal structure. The standard unit of density is kg m−3. Examples of the relative densities of various minerals compared with water at room temperature (about 1000 kg m−3) are shown in Table 1. The relationship between density and crystal structure is explored further in Section 4.

Table 1 Relative densities of various minerals.
Mineral Symbol/formula

Relative density at room conditions

(compared with water = 1.0)

Graphite C2.2
QuartzSiO22.65
DiamondC3.5
BariteBaSO44.5
GalenaPbS7.6
SilverAg10.5
GoldAu19.3
• According to the information provided in the Digital Geology Kit [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] , which of the following minerals has the highest density and which has the lowest density: garnet, gypsum and quartz?

• Garnet has the highest density (3.6-4.3); gypsum has the lowest density (2.3). Quartz is in between (2.65). (Density values quoted are relative to water.)