In mineralogy, quartz is one of the most common rock forming minerals. Quartz is composed mainly of which two chemical elements?

Introduction / Context:
Quartz is one of the most abundant and important minerals in the Earth crust, widely studied in geology and geography. Understanding its chemical composition helps learners grasp basic mineral classification and the dominance of certain elements in crustal rocks. This question asks you to identify the two main elements that form quartz, a common rock forming mineral found in many igneous, metamorphic, and sedimentary rocks.

Given Data / Assumptions:

• The mineral in question is quartz.
• We are choosing two elements that make up quartz.
• Options mix various combinations of iron, magnesium, oxygen, and silicon.
• We assume basic knowledge that quartz chemical formula is SiO2.

Concept / Approach:
Chemically, quartz is silicon dioxide, with the formula SiO2. This means each unit of quartz is made up of one silicon atom and two oxygen atoms bonded together. There is no iron or magnesium in pure quartz; those elements are found in other silicate minerals such as olivine or pyroxenes. Therefore, the two elements that compose quartz are silicon and oxygen. Among the options, the correct pair is oxygen and silicon.

Step-by-Step Solution:
Step 1: Recall the chemical formula of quartz, which is SiO2, representing silicon dioxide. Step 2: From the formula, identify the elements present: Si stands for silicon and O stands for oxygen. Step 3: Check each option. Iron and magnesium occur in many dark coloured minerals but are not components of pure quartz. Step 4: Iron and oxygen form oxides such as hematite and magnetite, not quartz. Step 5: Oxygen and silicon together accurately represent the elements in SiO2, the correct composition of quartz. Step 6: Silicon and iron together could form silicate minerals with iron content, but that is not quartz; so this option is incorrect. Step 7: Therefore, select oxygen and silicon as the two elements that compose quartz.

Verification / Alternative check:
Mineralogy references and basic chemistry texts confirm that quartz is silicon dioxide, SiO2, and belongs to the silicate group of minerals. Thin section microscopy, X ray diffraction, and chemical analysis all support this composition. The presence of silicon and oxygen is a hallmark of many crustal minerals, but quartz is a particularly simple example that contains only these two elements, with no iron or magnesium in the ideal structure. This confirms that oxygen and silicon is the correct pair.

Why Other Options Are Wrong:

• Iron and magnesium: These two elements commonly appear together in mafic minerals like olivine and pyroxene, but not in the composition of quartz.
• Iron and oxygen: Form iron oxides such as hematite, not silicon dioxide.
• Silicon and iron: Could describe some silicate minerals with iron content but does not match the pure quartz formula SiO2.

Common Pitfalls:
Some learners may over associate quartz with coloured or impure varieties and mistakenly think iron is part of its composition, since iron impurities can cause colours in some quartz types. Others may simply guess among the options without recalling the chemical formula. To avoid mistakes, memorise that quartz is SiO2, which directly tells you that the elements involved are silicon and oxygen only.

Final Answer:
Quartz is composed mainly of oxygen and silicon.