Question

Which of the following is not a Mg ore? (a) Magnesite (b) Gypsum (c) Carnalite (d) Dolomite

Short answer

Gypsum (b) is not a Mg ore.

Step-by-step solution

Identify the Mineral Components

To solve this problem, first understand what ores are. Ores are naturally occurring solid materials from which a metal can be extracted profitably. In this question, we need to identify which of the given mineral choices do not contain magnesium (Mg) as the main extractable metal.

Examine Each Option for Mg Content

Let's examine each listed mineral for Mg content. - **Magnesite**: MgCO₃, contains a significant amount of Mg. - **Gypsum**: CaSO₄·2H₂O, contains calcium but no significant magnesium. - **Carnalite**: KMgCl₃·6H₂O, contains magnesium. - **Dolomite**: CaMg(CO₃)₂, contains magnesium.

Determine Which is Not a Mg Ore

From the above analysis, we see that Gypsum (CaSO₄·2H₂O) does not contain magnesium as a major component, whereas the others do contain significant amounts of magnesium. Therefore, Gypsum is not a magnesium ore.

Key concepts

Mineral Identification

Minerals are the building blocks of rocks and are defined by their unique physical and chemical properties. Identifying minerals involves examining their various characteristics such as color, hardness, cleavage, and specific gravity. To identify a mineral correctly, geologists often use a combination of tests:

• **Color and Luster**: This is the most apparent characteristic though not very reliable on its own since many minerals share similar colors.
• **Hardness**: Measured using the Mohs scale, this determines how easily a mineral can scratch or be scratched by other substances.
• **Streak**: The color of the powder produced when a mineral is dragged across a porcelain plate.
• **Density and Specific Gravity**: Provide insights into the mineral's composition and structure.

By applying these tests, we can accurately identify minerals and determine their potential as ores from which metals such as magnesium can be extracted.

Chemical Composition of Minerals

Minerals are defined by a definitive chemical composition and crystal structure. This composition allows scientists to classify and understand the processes that form them.Each mineral is composed of a specific combination of elements:

• **Magnesite**: Chemically represented as \( \text{MgCO}_3 \), consists predominantly of magnesium paired with carbonate.
• **Gypsum**: Has the formula \( \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \), containing calcium bound with sulfate and water molecules.
• **Carnalite**: \( \text{KMgCl}_3 \cdot 6\text{H}_2\text{O} \), which has magnesium, potassium, and chloride ions creating a hydrous mineral.
• **Dolomite**: Denoted by \( \text{CaMg(CO}_3)_2 \), containing a mix of calcium and magnesium carbonates.

Understanding these formulas is crucial for determining their uses, including which minerals qualify as magnesium ores.

Magnesium Extraction

Magnesium is a valuable metal, widely used due to its lightweight properties and strength. Extracting magnesium from its various ores involves multiple steps. The extraction process typically involves:

• **Mining the Ore**: The selection of ores like magnesite or dolomite involves mining and collection.
• **Beneficiation**: This pre-refinement stage involves crushing and sorting to increase magnesium concentration.
• **Chemical Reduction**: Often done via processes like electrolysis, where magnesium chloride is converted to magnesium.

This process yields magnesium metal suitable for uses ranging from aircraft construction to healthcare applications. Importantly, identifying non-magnesium ores, such as gypsum, prevents inefficiencies in extraction and production. This understanding highlights the critical first step of mineral identification in the extraction industry.