Minerals: Properties, Classification, and Extraction

Understanding Minerals: Definition & Properties

A mineral is a naturally occurring solid substance, not produced by living organisms, characterized by a specific chemical composition and an ordered atomic structure. There are approximately 4,000 different minerals, and their identification requires studying various properties.

Key Characteristics of Minerals

• Solid Substance: This criterion excludes all liquids and gases, such as seawater or air.
• Natural Origin: Any product manufactured by humans is excluded.
• Not Produced by Living Organisms: This rule excludes biological products like shells or pearls.
• Specific Chemical Composition: Each mineral possesses a unique and defined chemical formula.

Identifying Mineral Properties

Some characteristic properties used for mineral identification include:

• Form (Crystal Habit): The characteristic shape and size in which a mineral typically grows. A unique property of minerals is that if a sample is broken, its shape and size change, but each piece retains the same mineral identity.
• Color: A useful property for identifying minerals with a distinctive color. For example, sulfur is yellow, malachite is green, and galena is lead-gray.
• Luster: Describes the appearance of a mineral's surface in reflected light. To classify luster, names of familiar objects with similar reflective qualities are often used (e.g., metallic, vitreous, pearly).

Mineral Hardness: The Mohs Scale

Hardness is measured using the Mohs Scale of Mineral Hardness, which ranges from 1 to 10 based on reference minerals, from talc (softest) to diamond (hardest).

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

Major Mineral Groups and Examples

Silicate Minerals

Silicates constitute approximately 75% of the Earth's crust. All silicate minerals are composed of silicon and oxygen, often with other elements. Key examples include:

• Orthoclase: Has a hardness of 6, vitreous luster, and is white. It belongs to the feldspar group.
• Plagioclase: Also has a hardness of 6, vitreous luster, and is white. It also belongs to the feldspar group.
• Quartz: With a hardness of 7 and vitreous luster, quartz can exhibit various colors. After feldspars, it is the most abundant mineral.
• Muscovite (White Mica): Has a hardness of 3 and a pearly luster. It is easily identified by its cleavage into thin sheets. (Biotite is a dark mica).
• Olivine: Has a hardness of 6.5, vitreous luster, and its characteristic olive-green color gives it its name.

Other Important Minerals

While many rocks are primarily formed by silicates, other significant minerals exist:

• Talc: Has a hardness of 1-2 and is typically white. It sometimes has a fibrous appearance.
• Calcite: Has a hardness of 3, ranges from white to brown, and releases bubbles when exposed to acids like hydrochloric acid or vinegar.
• Halite: Has a hardness of 2.5 and is a colorless or white salt. It is commonly known as table salt and used as a cooking condiment.

Mining Operations: Types of Mines

The type of mine depends on the depth at which the mineral deposit is found:

• Open-Pit Mines: These are excavations where the mineral deposit is found very close to the surface. The most important examples are quarries, where materials for construction, ornamentation, and rocks are extracted.
• Shaft Mines: These are deep or medium-sized mines, very common in metallic mineral operations. They are structured in terraces at increasing depths.
• Underground Mines: These are excavations located deep underground. They consist of a network of tunnels. The horizontal tunnels are called galleries or drifts, and the vertical ones are shafts.

Extracting Metals from Ores

Few metals are found in their native or pure state. Usually, they appear combined with other elements, forming ores. For example, hematite contains iron and oxygen; chalcopyrite contains copper and sulfur.

To extract the desired metal, a specific process is initiated, beginning at the mineral deposit itself.