Olivine

Definition

Olivine is a common mineral found in Earth's mantle, primarily composed of magnesium iron silicate. It is an essential component of mafic and ultramafic rocks and plays a crucial role in understanding the composition and processes occurring within the Earth's interior.

5 Must Know Facts For Your Next Test

1. Olivine crystallizes in a orthorhombic structure and is usually green, ranging from yellow-green to dark green in color.
2. It has a high melting point, making it stable at high temperatures and pressures typically found in the Earth's mantle.
3. Olivine is often used as a gemstone in its transparent form, known as peridot, which is the birthstone for August.
4. The presence of olivine in basaltic lava suggests that it forms at high temperatures in volcanic environments.
5. Olivine can undergo a process called metamorphism, transforming into other minerals like serpentine under certain conditions.

Review Questions

• How does the presence of olivine in rocks like basalt inform us about the conditions under which these rocks were formed?
  • The presence of olivine in rocks such as basalt indicates that these rocks formed under high temperature conditions, typical of magma originating from the Earth's mantle. Since olivine has a high melting point and is stable at elevated temperatures, its existence suggests that the basalt crystallized from molten rock that cooled relatively quickly after eruption. This relationship helps geologists infer the thermal history of volcanic rocks and their source material.
• Discuss the significance of olivine in understanding the composition and dynamics of the Earth's mantle.
  • Olivine is a significant mineral for understanding the Earth's mantle due to its abundance and stability at high pressures. As one of the primary minerals present in peridotite, it serves as an indicator of the mantle's mineralogical composition. Studying olivine helps scientists interpret mantle convection processes, as it contributes to our knowledge of how heat and materials are transferred within this layer, which ultimately influences plate tectonics and volcanic activity.
• Evaluate the role of olivine in both geological processes and practical applications, including its use as a gemstone.
  • Olivine plays a dual role in geological processes and practical applications. Geologically, it provides insights into the formation and evolution of mafic and ultramafic rocks within the Earth's mantle. Its presence indicates specific temperature and pressure conditions during rock formation. Practically, olivine's transparent form, known as peridot, is valued as a gemstone for jewelry, showcasing its aesthetic appeal while also linking back to geological processes. Understanding olivine's characteristics allows us to appreciate both its scientific importance and its value in consumer markets.

Related terms

Mantle: The layer of the Earth located between the crust and the core, made up of solid rock that can flow slowly over time.

Basalt: A dark, fine-grained igneous rock that is primarily composed of plagioclase and pyroxene, often containing olivine as well.

Peridotite: A dense, coarse-grained igneous rock consisting predominantly of olivine and pyroxene, commonly found in the Earth's mantle.