Bowen's Reaction Series #3 - Pyroxenes!

The next mineral to form on the discontinuous branch of Bowen's Reaction Series, pyroxenes, hold a special place in my heart - my undergraduate petrology research focused on geochemical analyses of clinopyroxenes in igneous arc rocks! 

Pyroxenes are a crucial minerals in the study of igneous rocks and crust formation. But where does pyroxene fit in Bowen's Reaction Series, and why is it so important in geology?

What is Bowen's Reaction Series?

Bowen's Reaction Series is a classification scheme that illustrates the order in which minerals crystallize from a cooling magma. It helps geologists understand the sequence of mineral formation and the relationship between different minerals in igneous rocks. If you need a refresher, check out this post from the start of the series: Bowen's Reaction Series

Where does Pyroxene Fit in Bowen's Reaction Series?

Pyroxene is a key mineral in the discontinuous branch of Bowen's Reaction Series. It crystallizes early in the cooling process of a magma, after olivine, but before amphibole. This makes pyroxene an essential indicator of the magma's composition and cooling history.

The general chemical formula for pyroxenes [(Na,Ca)(Mg,Fe,Al)(Al,Si)₂O₆] show how they have similar cations to the less complex pyroxene, but now at a cooler temperature, develop a more complex silicate structure. Depending upon the concentration of the different cations (Na, Ca, Mg, Fe, Al) as well as the pressure & temperature conditions of a magma, slightly different minerals in the pyroxene family can be formed (illustrated in the ternary diagram below).

Why is Pyroxene Important in Understanding Igneous Rocks?

Pyroxene provides valuable information about the origin and evolution of igneous rocks. By studying the presence and composition of pyroxene in a rock sample, geologists can determine the rock's cooling rate, magma source, and tectonic setting. This knowledge is crucial for understanding the Earth's geological history and processes.

What Can Pyroxene Be Used For?

Pyroxene has various practical applications beyond its role in geology, although typically is not very valuable on its own. It is used in the manufacturing of ceramics, glass, and certain types of concrete and can be used as an abrasive for finishing soft materials. Occasionally, gem quality specimens can be found, and these can command a high price due to their rarity. 

Overall, pyroxene plays a significant role in the study of igneous rocks, crust formation, and geological processes. Its placement in Bowen's Reaction Series, along with its applications in various industries, highlights the importance of this mineral in both scientific research and everyday life.