How do minerals crystallize from magma?

Minerals crystallize from magma as it cools, a process governed by the chemical composition of the melt and the rate of temperature decrease. This systematic formation is described by Bowen’s reaction series, which outlines how minerals form in both continuous and discontinuous sequences as magma cools.12

• Discontinuous Series: Minerals such as olivine, pyroxene, amphibole, and biotite crystallize at specific temperatures, with earlier-formed minerals reacting with the remaining liquid to form more stable crystals at lower temperatures.12
• Continuous Series: Plagioclase feldspar reacts continuously with the liquid, gradually changing its composition from calcium-rich to sodium-rich as the temperature drops.12

The rate of cooling significantly influences the final texture: rapid cooling (such as in volcanic lava) results in tiny grains or glass, while slow cooling underground allows for the growth of larger, visible crystals. Additionally, fractional crystallization can occur if early-formed, dense crystals are removed from the liquid, preventing further reaction and altering the composition of the remaining magma. In some cases, cooling magma may also precipitate immiscible liquid droplets, which can lead to the formation of distinct ore deposits.3425