Question

consider the following statements analyze the elemental composition of the minerals: Which of the statements is/are correct?

1. Silica is a common component found in Pyroxene, Amphibole, Mica, and Olivine.
2. Potassium is found in both Mica and Pyroxene.
3. Magnesium and Iron are present in all four minerals listed.

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

Answer 1

Answer:

D. i, iii

Elemental Composition of Common Minerals

• Statement I: Silica as a Common Component

  • Silica (SiO₂) is a fundamental building block for most silicate minerals.

  • Minerals like Pyroxene, Amphibole, Mica, and Olivine are all classified as silicates, meaning their crystal structure is based on silicon-oxygen tetrahedra.

  • Therefore, silica is indeed a common and essential component in all four of these mineral groups.

• Statement II: Potassium in Mica and Pyroxene

  • Mica group minerals (e.g., Muscovite, Biotite) often contain potassium (K), especially in their layered structures.

  • Pyroxene group minerals, which have single-chain silicate structures, typically contain cations like calcium (Ca), sodium (Na), magnesium (Mg), and iron (Fe). While some rare pyroxenes might incorporate potassium, it is not a characteristic or common element found in the general composition of pyroxenes.

  • Therefore, the statement that potassium is found in both Mica and Pyroxene is generally incorrect for Pyroxene.

• Statement III: Magnesium and Iron Presence

  • Olivine is a nesosilicate with the general formula (Mg, Fe)₂SiO₄, making magnesium and iron key components.

  • Pyroxenes are inosilicates with formulas often including Mg and Fe, such as Enstatite (MgSiO₃) and Ferrosilite (FeSiO₃), and their solid solutions.

  • Amphiboles, also inosilicates, commonly contain magnesium and iron, with general formulas often showing (Mg, Fe)₇Si₈O₂₂(OH)₂.

  • Micas, phyllosilicates, also incorporate magnesium and iron, particularly in biotite (a 'dark' mica) which has a composition including K(Mg,Fe)₃AlSi₃O₁₀(OH)₂.

  • Thus, magnesium and iron are characteristic and frequently present elements in all four listed mineral groups.