Essential Mineral Properties and Classification Methods

Fundamentals of Mineralogy

Defining Minerals

Minerals are solid chemical combinations of elements that exist naturally in the Earth's crust.

Key Characteristics

• Solid
• Natural
• Inorganic
• Homogeneous

Composition and Structure

• Composition: Pure substances.
• Impurities: Altering properties of the mineral (resulting in varieties).
• Amorphous: The mineral components are disordered.
• Crystallized: The mineral components are ordered, having flat faces, vertices, and edges (forming crystals).

Classification by Chemical Group

• Silicates: A group of minerals whose main components are silicon and oxygen. E.g., quartz, feldspars, micas, clay minerals, olivine.
• Non-silicates: A group of minerals that do not contain silicon. E.g., native elements, oxides, sulfides, sulfates, carbonates, halides.

Origin of Minerals

• Formed in a mass of molten rock (magma). E.g., feldspars, olivine.
• Formed in solid rocks under high pressures and temperatures. E.g., Muscovite.
• Crystallization of dissolved substances in water. E.g., gypsum, calcite.

Physical Properties of Minerals

These properties help in the identification and classification of mineral specimens:

• Color: The type of light the mineral reflects when illuminated with white light.
• Luster: The way the mineral reflects light. Can be: metallic, oily, vitreous, greasy, and dull.
• Hardness: The resistance of the mineral to being scratched.
• Streak (Color Line): The color left by the mineral when rubbed against an unglazed porcelain surface.
• Cleavage (Exfoliation): The property of breaking into fragments that retain flat faces.

The Mohs Scale of Hardness

The Mohs Scale is used for classifying minerals based on their relative hardness. It consists of 10 reference minerals, from talc (softest) to diamond (hardest). A mineral can only scratch another if it has equal or greater hardness.

Mohs Scale Reference Minerals (1-10)

1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Orthoclase
7. Quartz
8. Topaz
9. Corundum
10. Diamond

Applications and Extraction

Uses of Minerals

• Metal Extraction: Source of valuable metals. E.g., Galena (for lead), Sphalerite (for zinc), Cinnabar (for mercury).
• Ceramic Industries: Used in manufacturing. E.g., clay minerals for ceramics and bricks.
• Construction Materials: Used in building. E.g., gypsum (plaster), calcite (cement), quartz (glass).
• Jewelry: Precious materials used for adornment. E.g., gold, silver, platinum, diamond.

Mineral Extraction Methods

• Open-Pit Operations: Used when the deposit is located at shallow depth. These are often called quarries.
• Mine (Underground Mining): Used when the deposit is located at a great depth. This is a very dangerous job.