Pyroxene

Definition

Pyroxene is a group of important rock-forming minerals that are primarily composed of silicate, exhibiting a range of compositions and structures. These minerals are typically found in igneous and metamorphic rocks, playing a key role in the geological processes that shape Earth's crust. They are characterized by their elongated crystals and often dark colors, contributing to the overall composition and texture of various rocks.

5 Must Know Facts For Your Next Test

1. Pyroxenes are classified into two main groups: clinopyroxenes and orthopyroxenes, based on their crystal structure and composition.
2. These minerals are commonly found in basalt and granite, where they influence the properties and behavior of these rocks.
3. Pyroxene can be identified by its distinctive cleavage at 87 and 93 degrees, which helps distinguish it from other mineral groups.
4. In addition to being significant in terrestrial geology, pyroxenes are also important for understanding the mineralogy of extraterrestrial bodies, like the Moon and Mars.
5. The presence of pyroxene in a rock can indicate its formation environment, helping geologists infer the temperature and pressure conditions during its creation.

Review Questions

• How do pyroxenes contribute to the identification and classification of different types of igneous rocks?
  • Pyroxenes are critical in identifying and classifying igneous rocks because their presence, type, and abundance can provide insights into the rock's origin and formation conditions. For example, the dominance of clinopyroxene versus orthopyroxene can indicate whether a rock formed from magma with higher or lower temperatures. Additionally, the specific compositions of pyroxenes can help distinguish between different volcanic rock types, such as basalt or rhyolite.
• Discuss the role of pyroxene in understanding metamorphic processes within Earth's crust.
  • Pyroxene plays a significant role in metamorphic processes as it is often formed under high-temperature and high-pressure conditions. The presence of pyroxene in metamorphic rocks can indicate specific metamorphic environments, such as contact or regional metamorphism. Furthermore, studying the composition and texture of pyroxene within these rocks helps geologists reconstruct the temperature and pressure history that led to their formation, offering insights into tectonic activities.
• Evaluate how the study of pyroxenes enhances our knowledge of planetary geology beyond Earth.
  • The study of pyroxenes extends our understanding of planetary geology by providing valuable information about the mineralogical compositions on other celestial bodies. For instance, analyzing pyroxene spectra from lunar samples or Martian rovers helps scientists infer past volcanic activity and geological processes on these planets. By comparing terrestrial pyroxene compositions with those found on the Moon or Mars, researchers can develop theories about the formation histories and geological evolution of these planetary bodies.

Related terms

Igneous Rocks: Rocks formed through the cooling and solidification of magma or lava, where pyroxenes commonly occur.

Silicate Minerals: The largest group of minerals, which include pyroxenes, characterized by the presence of silicon and oxygen in their structure.

Metamorphic Rocks: Rocks that have undergone transformation due to heat, pressure, or chemically active fluids, often containing pyroxene as a result.