Question

Which mineral is characterized by being found in meteorites and constitutes exactly 10% of the Earth's crust?

• A. Olivine
• B. Amphibole
• C. Pyroxene
• D. Mica

Answer 1

Answer:

C. Pyroxene

Pyroxene Group Minerals

Pyroxenes are a group of inosilicate minerals forming an important component of igneous and metamorphic rocks. They are characterized by their chemical formula which generally involves chains of SiO₄ tetrahedra linked by ions such as iron (Fe), magnesium (Mg), calcium (Ca), and aluminum (Al).

Key Characteristics and Significance

• Abundance in Earth's Crust: Pyroxenes constitute approximately 10% of the Earth's crust by weight, making them one of the most abundant mineral groups. They are particularly prevalent in mafic and ultramafic igneous rocks like basalt and gabbro, which form a significant part of the oceanic crust and continental volcanic regions.

• Presence in Meteorites: Pyroxenes are also found in meteorites, including stony meteorites (chondrites and achondrites), which provides insights into the composition of the early solar system and extraterrestrial materials. This extraterrestrial presence is a unique characteristic that distinguishes them from some other common crustal minerals.

• Geological Formation: They are typically formed under high temperatures and pressures, often found in mantle-derived magmas and deep crustal environments.

• Structural Feature: Their crystal structure features single chains of linked SiO₄ tetrahedra, which gives them their characteristic prismatic cleavage angle of around 87° and 93°.

• Types of Pyroxenes: Common examples include enstatite (MgSiO₃), ferrosilite (FeSiO₃), and diopside (CaMgSi₂O₆). The solid solution series between these end-members leads to a wide variety of pyroxene compositions.