Geology Mineralogy MCQ Solution: Identifying Correct Statements

This multiple-choice question asks us to identify the single correct statement about specific minerals and geological terms from the options provided. Let's analyze each statement in detail.

Statement 1: Pyroxene is commonly found in meteorites

Pyroxenes are a significant group of silicate minerals, characterized by single chains of silica tetrahedra. They are essential components of many igneous rocks, especially mafic and ultramafic ones, and are also found in metamorphic rocks. Their presence is widespread in the Earth's crust and mantle.

Regarding meteorites, various types contain pyroxenes. For instance, chondrites, which are primitive meteorites, often show abundant pyroxene minerals. Their composition in meteorites helps scientists understand the conditions under which these extraterrestrial materials formed and evolved.

Conclusion: This statement is factually correct.

Statement 2: Amphiboles form about 20% of the Earth's crust

Amphiboles are another group of silicate minerals, distinguished by their double-chain structure and the presence of hydroxyl ions (OH). They are common constituents of igneous and metamorphic rocks, often occurring alongside pyroxenes.

However, the abundance of amphiboles in the Earth's crust is significantly less than 20%. Feldspars are the most abundant mineral group, making up roughly 50% of the crust, followed by quartz (about 12%). Amphiboles constitute a smaller fraction, generally estimated to be less than 10% of the Earth's crust by volume.

Conclusion: This statement is incorrect.

Statement 3: Quartz is soluble in water

Quartz is a mineral composed of silicon dioxide (SiO₂). It is extremely common, forming the basis of many rocks like granite and sandstone. It is known for its hardness and chemical stability.

Quartz exhibits very low solubility in pure water under standard surface conditions. While it can undergo very slow chemical weathering over geological time or dissolve under specific conditions (like high temperature, pressure, or in the presence of certain aggressive chemical agents like strong alkaline solutions), it is considered practically insoluble in everyday water.

Conclusion: This statement is incorrect.

Statement 4: The word 'sedimentary' is derived from the Latin word kelimentum

Sedimentary rocks are formed through the process of sedimentation, where particles like sand, silt, and clay accumulate and are later cemented together.

The term 'sedimentary' originates from the Latin word 'sedimentum', which means 'a settling' or 'sediment'. The Latin word 'elementum' means 'first principle' or 'rudiment'. Thus, the statement incorrectly cites the origin of the word 'sedimentary'.

Conclusion: This statement is incorrect.

Final Conclusion

After evaluating each option based on established geological facts, the only statement that accurately describes the subject matter is that pyroxene is commonly found in meteorites.