Question

Consider the following regarding Mica and Olivine, which of the following is true?

1. Mica is found in both Igneous and Metamorphic rocks.
2. Olivine contains Calcium as a main component.
3. Mica's crustal abundance is lower than that of Pyroxene.

• A. 1 only
• B. All
• C. 1, 2
• D. 1, 3

Answer 1

Answer:

D. 1, 3

• Mica: Mica is a group of sheet silicate (phyllosilicate) minerals. It is commonly found in igneous (like granite and pegmatite) and metamorphic rocks (like gneiss and schist). Its presence in these rock types is due to the processes of magma crystallization and recrystallization under heat and pressure.
• Olivine: Olivine is a magnesium iron silicate mineral with the formula (Mg, Fe)₂SiO₄. It does not contain Calcium as a main component. Its primary constituents are magnesium, iron, silicon, and oxygen.
• Crustal Abundance: Relative to other common rock-forming minerals, mica's crustal abundance is significant. However, Pyroxenes form a larger group of minerals and are generally more abundant in the Earth's crust than micas. Pyroxenes are important constituents of mafic and ultramafic igneous rocks.
• Exam Relevance: Understanding the rock types in which specific minerals occur and their relative abundance in the Earth's crust are common topics in geology and geography-related competitive exams. Pay attention to the chemical composition and mineral classification of common geological materials.