Olivine

Definition

Olivine is a common silicate mineral composed of magnesium iron silicate, represented by the formula (Mg, Fe)₂SiO₄. It typically occurs in igneous rocks, particularly basalt and peridotite, and plays a crucial role in understanding the formation and classification of these rocks, as well as the processes that occur during magma differentiation.

5 Must Know Facts For Your Next Test

1. Olivine is one of the first minerals to crystallize from molten rock according to Bowen's Reaction Series, forming at high temperatures.
2. The color of olivine can range from olive green to yellowish-green, which is often used to identify it in hand specimens.
3. As a major component of peridotite, olivine provides insights into the composition of the Earth's upper mantle.
4. In basaltic lavas, olivine can become a phenocryst, meaning it crystallizes earlier and is visible as larger crystals within the finer-grained matrix.
5. Olivine weathers relatively quickly on the Earth's surface compared to other minerals, contributing to soil formation and nutrient cycles.

Review Questions

• How does olivine's crystallization temperature relate to its role in igneous rock formation?
  • Olivine crystallizes at higher temperatures compared to other common minerals like feldspar and quartz. This characteristic places it early in Bowen's Reaction Series, indicating that it forms during the initial stages of magma cooling. Its presence in igneous rocks such as basalt and peridotite helps geologists understand the conditions under which these rocks formed and how they are classified based on mineral composition.
• What implications does olivine's presence have on magma differentiation processes?
  • The presence of olivine in magma indicates that it may have undergone specific differentiation processes. As olivine crystallizes from magma, it can remove magnesium and iron from the melt, leading to changes in the composition of the remaining liquid. This process can affect the overall mineralogy of the resulting rock and lead to variations such as more evolved compositions like granite, which contain minerals that crystallize at lower temperatures.
• Evaluate how olivine contributes to our understanding of mantle composition and its impact on volcanic activity.
  • Olivine is a key indicator of mantle composition since it is one of the primary minerals found in peridotite, which constitutes much of the Earth's upper mantle. By studying olivine in volcanic rocks like basalt, scientists gain insights into the conditions under which magma forms and ascends from the mantle. This understanding can help predict volcanic activity by revealing information about magma generation processes and the potential for eruption based on mantle characteristics.

Related terms

Basalt: A dark-colored, fine-grained igneous rock that is rich in magnesium and iron, commonly formed from the rapid cooling of basaltic lava.

Peridotite: A dense, coarse-grained igneous rock composed primarily of olivine and pyroxene, typically found in the Earth's mantle.

Magma Differentiation: The process by which different minerals crystallize from cooling magma at different temperatures, leading to the formation of diverse rock types.