Minerals form from solutions when dissolved ions precipitate out as the solution becomes supersaturated. Conditions such as temperature and pressure changes contribute to the formation of minerals like fluorite, which may contain impurities that give them color.
Minerals can form from solutions when the conditions are right for precipitation. This occurs when dissolved ions in groundwater become supersaturated, leading them to combine and solidify out of the solution. An example is the mineral fluorite (CaF2), where dissolved calcium and fluoride ions in groundwater precipitate within the Earth's crust to form crystals. If other metal ions are present, they can give color to otherwise colorless fluorite.
Conditions for mineral formation from solutions include changes in temperature, pressure, or evaporation rates—causing solutions to become supersaturated. As illustrated by Figure 15.1, pure fluorite is colorless, but the presence of impurities such as other metal ions can provide vibrant colors to the crystals.
So, minerals like fluorite crystallize from solutions when the solubility limits are exceeded, leading to the formation of solid compounds.