Question

An important ore of magnesium is: (a) Malachite (b) Cassiterite (c) Carnalite (d) Galena

Short answer

The important ore of magnesium is (c) Carnalite.

Step-by-step solution

Understand the Question

The question asks us to identify which among the given options is an important ore of magnesium. An ore is a naturally occurring solid material from which a metal or valuable mineral can be extracted.

Identify the Options

Look at the options provided: (a) Malachite, (b) Cassiterite, (c) Carnalite, (d) Galena. We need to determine which of these is associated with magnesium.

Recognize Ores and Their Elements

Recall the common elements associated with each ore: - Malachite is a source of copper. - Cassiterite is an ore of tin. - Carnalite is a mineral of magnesium. - Galena is a primary ore of lead.

Select the Correct Option

Based on the information in Step 3, Carnalite is the ore associated with magnesium. The others are ores of different elements.

Key concepts

Carnalite

Carnalite is an important mineral known as an ore of magnesium. It is a naturally occurring mineral compound with the chemical formula \( KCl \cdot MgCl_2 \cdot 6H_2O \). Carnalite is a hydrated potassium magnesium chloride. It plays a crucial role in the extraction of magnesium, as it contains magnesium in an easily extractable form. This mineral often appears as yellow to whitish and is usually found in sedimentary evaporite deposits along with other minerals like halite.

In terms of geology, carnalite typically forms in arid environments where evaporation rates are high and water is rapidly lost, leaving behind layers of mineral deposits.

• Important Source: Carnalite is a major source of magnesium and is extensively mined for commercial use.
• Occurrence: It is mined primarily in areas such as Germany, the United States, and the Dead Sea region.

By understanding the characteristics of carnalite, students can better identify it among minerals and appreciate its significance in magnesium extraction.

Magnesium Extraction

The extraction of magnesium involves several key processes to isolate this reactive metal from its ores like carnalite. Magnesium is typically extracted through electrolytic or thermal reduction methods.

In the electrolytic process, carnalite is first dissolved in water and subjected to electrolysis, where electricity is used to separate the magnesium from chlorine gas. This process is effective because magnesium chloride, found in carnalite, dissociates into magnesium and chlorine under the influence of an electric current. This method is popular due to its efficiency in producing pure magnesium.

The thermal reduction method, often referred to as the "Pidgeon process," involves reducing magnesium from dolomite or carnalite using silicon in high temperatures within a vacuum. Despite being more traditional, this method is still widely used in areas where electricity costs are high.

• Electrolytic Process: Utilizes electricity to extract magnesium.
• Thermal (Pidgeon) Process: Involves high-temperature reduction of magnesium.

Understanding these methods helps students appreciate the complexities involved in isolating magnesium for industrial uses.

Mineral Identification

Identifying minerals such as carnalite involves understanding various physical and chemical properties. This process is crucial for geologists and students alike to correctly determine a mineral's identity and economic relevance.

Key properties used in mineral identification include color, luster, hardness, and crystal form. For instance, carnalite is typically identified by its yellowish to white color and its vitreous to pearly luster. It also crystallizes in the orthorhombic system, which helps distinguish it from other similar-looking minerals.

• Color and Luster: Carnalite can be yellowish to whitish with a shiny surface.
• Hardness: It is relatively soft and can be scratched by common objects.
• Crystal Structure: Forms in the orthorhombic system, providing a unique physical blueprint for identification.

Learning to identify minerals through these characteristics not only enhances one's understanding of earth sciences but also aids in their practical applications in industry and research.