Consider the following statements:

I. Silicon and oxygen are common elements in all types of feldspar and sodium, potassium, calcium, aluminium etc. are found in specific feldspar variety.

II. Almost one-fourth of the Earth's crust is composed of feldspar and quartz.

Which of the above statements is/are correct? 

Key Points

• Feldspar is a group of minerals that are very common in the Earth's crust.
• Feldspar minerals are composed of silicon and oxygen in combination with other elements such as sodium, potassium, calcium, and aluminium.
• These additional elements are found in specific varieties of feldspar.
• Statement I is correct because it accurately describes the composition of feldspar minerals.

Additional Information

• Feldspar:
  • Feldspar is the name given to a group of minerals distinguished by the presence of aluminum and the silica (SiO₄) tetrahedron.
  • They form under varying conditions and are found in many types of rock, such as igneous, metamorphic, and sedimentary rocks.
  • Feldspars are divided into two main groups: potassium feldspars (orthoclase, microcline) and plagioclase feldspars (albite, anorthite).
• Quartz:
  • Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms.
  • It is the second most abundant mineral in the Earth's continental crust, after feldspar.
  • Quartz is highly resistant to weathering and is commonly found in sand and sandstone.
• Earth's Crust:
  • The Earth's crust is the outermost layer of the planet, making up less than 1% of Earth's volume.
  • The crust is composed of a variety of rock types, including igneous, metamorphic, and sedimentary rocks.
  • While feldspar and quartz are indeed abundant in the Earth's crust, almost one-fourth is an overstatement.