Question

Consider the following statements regarding Pyroxene:

1. It is commonly found in meteorites.
2. Its color is generally pale white or salmon pink.
3. The main elements in pyroxene include calcium, iron, and silica.

• A. i, iii
• B. iii only
• C. i only
• D. ii, iii

Answer 1

Answer:

A. i, iii

Pyroxene

Mineral Group and Structure:

• Pyroxenes are a group of inosilicate minerals, meaning their crystal structure is characterized by single chains of silica tetrahedra. This contrasts with amphiboles, which have double chains.

• The general formula for pyroxenes is XYZ(Al,Si)₂O₆, where X, Y, and Z represent different cations (metal ions).

Key Elements:

• The main elements that constitute pyroxenes include silica (SiO₂), magnesium (Mg), and iron (Fe).

• Other common elements found in various pyroxene species are calcium (Ca), aluminum (Al), and sometimes sodium (Na) or manganese (Mn).

• Therefore, statements mentioning calcium, iron, and silica as main elements are generally correct for many common pyroxenes.

Coloration:

• The color of pyroxenes can vary widely depending on their chemical composition, particularly the iron content.

• Common colors include shades of green, brown, black, and even colorless or pale.

• While some pyroxenes might appear pale, salmon pink is not a typical or defining color for the group.

Occurrence:

• Pyroxenes are abundant minerals in the Earth's crust and upper mantle.

• They are particularly characteristic of mafic and ultramafic igneous rocks, such as basalt, gabbro, and peridotite.

• Meteorites are extraterrestrial objects that often contain minerals found in the solar system's early formation. Many common terrestrial minerals, including pyroxenes, are found in meteorites, especially in stony meteorites (chondrites and achondrites). Therefore, pyroxenes are indeed commonly found in meteorites.