Problem 17 - Chemistry in 30 days

Question

Which of the following minerals contains both \(\mathrm{Mg}\) and \(\mathrm{Ca}\) ? (a) Dolomite (b) Gypsum (c) Epsomite (d) Tale

Step-by-Step Solution

Answer

Dolomite contains both \(\mathrm{Mg}\) and \(\mathrm{Ca}\).

Step 1: Identifying Dolomite

Dolomite is a mineral composed of calcium magnesium carbonate, with a chemical formula of \( ext{CaMg(CO}_3 ext{)}_2\). This indicates the presence of both \( ext{Mg}\) and \( ext{Ca}\).

Step 2: Analyzing Gypsum

Gypsum is a mineral composed of calcium sulfate dihydrate, with the formula \( ext{CaSO}_4 imes 2 ext{H}_2 ext{O}\). It contains \( ext{Ca}\) but not \( ext{Mg}\).

Step 3: Checking Epsomite

Epsomite, commonly known as Epsom salt, is made of magnesium sulfate heptahydrate with the formula \( ext{MgSO}_4 imes 7 ext{H}_2 ext{O}\). It includes \( ext{Mg}\) but lacks \( ext{Ca}\).

Step 4: Evaluating Tale

The mineral talc has a formula \( ext{Mg}_3 ext{Si}_4 ext{O}_{10}(OH)_2\), composed of magnesium, silicon, and oxygen, but does not contain \( ext{Ca}\).

Step 5: Conclusion

Only dolomite contains both \( ext{Mg}\) and \( ext{Ca}\). Therefore, the correct answer is (a) Dolomite.

Key Concepts

Dolomite

Dolomite is an intriguing mineral often encountered in mineralogy studies. Named after the French geologist Déodat Gratet de Dolomieu, it is composed primarily of calcium magnesium carbonate with the chemical formula \(\text{CaMg(CO}_3\text{)}_2\). This dual composition is what makes dolomite special. It incorporates both calcium \((\text{Ca})\) and magnesium \((\text{Mg})\) into its structure.

This mineral is usually found in sedimentary rocks, particularly in dolostone. Dolomite can appear in a variety of colors, ranging from white and gray to pink and brown, often adding visual appeal to geological formations. On rare occasions, it can even display a pearly luster or exhibit iron and manganese, contributing to its color variations.

Dolomite plays an essential role in various industries. It is used in construction and as a source of magnesium oxide, which is important in producing refractory materials that withstand high temperatures. Its impressive versatility extends to agriculture, where it helps amend soil by neutralizing acidity.

Mineral Composition

Mineral composition refers to the chemical elements that make up a mineral. Understanding the composition is crucial for identifying minerals and understanding their properties.

Key Factors in Mineral Composition:

• Elements: Minerals are made from elements combined in specific arrangements. For example, dolomite consists of calcium \((\text{Ca})\) and magnesium \((\text{Mg})\) within carbonate \((\text{CO}_3)\).
• Crystal Structure: The way elements are arranged determines the mineral's crystal structure, influencing its physical properties.
• Chemical Formula: Provides a concise way to express the elements and their proportions in a mineral. For dolomite, the chemical formula is \(\text{CaMg(CO}_3\text{)}_2\).

These factors aid geologists and hobbyists alike in distinguishing one mineral from another by examining their unique composition and structure. This not only helps in identification but also guides their practical applications.

Calcium and Magnesium Minerals

Calcium and magnesium are two chemical elements frequently found in a variety of minerals.

Roles in Minerals:

• Calcium \((\text{Ca})\): Common in many minerals such as gypsum \((\text{CaSO}_4 \times 2\text{H}_2\text{O})\), contributing to their hardness and formation processes.
• Magnesium \((\text{Mg})\): Present in minerals like talc and epsomite \((\text{MgSO}_4 \times 7\text{H}_2\text{O})\), influencing their texture and appearance.
• Joint Occurrence: In minerals like dolomite, calcium and magnesium are combined, leading to a unique set of physical properties suitable for specific industrial applications.

Calcium and magnesium often determine the utility and extraction methods for the minerals in which they are present. These properties influence not only geological studies but also agricultural practices and industrial uses.