Olivine

Definition

Olivine is a magnesium iron silicate mineral that is commonly found in igneous rocks and is a significant component of the Earth's upper mantle. Its distinctive green color and granular appearance make it easily identifiable, and it plays a crucial role in understanding both the composition of the Earth and the classification of igneous rocks, particularly basalt and peridotite.

5 Must Know Facts For Your Next Test

1. Olivine is considered a primary mineral in mafic and ultramafic igneous rocks, making it essential for understanding the composition of the Earth's mantle.
2. The color of olivine can vary from olive green to yellowish-green depending on its iron content; higher iron content typically results in a darker hue.
3. It has a glassy luster and is often found in volcanic rocks, where it forms as lava cools quickly.
4. Olivine is resistant to weathering compared to other minerals, which helps it persist in certain environments even after other minerals have broken down.
5. The presence of olivine in rocks can indicate the conditions under which those rocks formed, including temperature and depth within the Earth.

Review Questions

• How does the presence of olivine in igneous rocks help us understand the processes occurring within the Earth's mantle?
  • The presence of olivine in igneous rocks indicates that these rocks have originated from high-temperature environments typical of the Earth's mantle. Olivine forms under specific pressure and temperature conditions, which can help geologists deduce the formation conditions of these rocks. By studying where olivine occurs, scientists can gain insights into mantle composition, temperature gradients, and even the tectonic processes occurring beneath Earth's surface.
• Discuss how olivine contributes to the classification of igneous rocks, particularly basalt and peridotite.
  • Olivine plays a key role in classifying igneous rocks such as basalt and peridotite. Basalt is often categorized as a mafic rock, characterized by a higher content of iron and magnesium minerals like olivine. In contrast, peridotite is an ultramafic rock primarily composed of olivine, making its presence crucial for identifying its formation environment. The specific mineral composition, including olivine content, aids in determining the rock's origin and evolution.
• Evaluate the significance of olivine's physical properties in identifying its occurrence in different geological environments.
  • Olivine's physical properties are vital for identifying its occurrence across various geological settings. Its characteristic green color and glassy luster allow for easy recognition among other minerals. Additionally, its durability against weathering enables it to survive in sedimentary environments where other minerals may break down. Understanding these properties can also aid scientists in deciphering past geological events by examining how and where olivine has been preserved in different rock formations.

Related terms

Basalt:

A fine-grained igneous rock that is primarily composed of pyroxene and plagioclase, often containing olivine, and is commonly found in oceanic crust.

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

Felsic: Describes a category of igneous rocks that are rich in lighter elements like silicon, oxygen, aluminum, sodium, and potassium, contrasting with mafic rocks that contain more iron and magnesium.