Question

Each of the following statements describes a silicate mineral or mineral group. In each case, provide the appropriate name: a. the most common member of the amphibole group b. the most common nonferromagnesian member of the mica family c. the only common silicate mineral made entirely of silicon and oxygen d. a high-temperature silicate with a name that is based on its color e. a silicate mineral that is characterized by striations f. a silicate mineral that originates as a product of chemical weathering

Short answer

a. Hornblende, b. Muscovite, c. Quartz, d. Olivine, e. Feldspar, f. Kaolinite.

Step-by-step solution

Identify the Amphibole Mineral

The most common member of the amphibole group is hornblende. Amphibole minerals generally contain silicate chains and occur in various rock formations.

Identify the Nonferromagnesian Mica

The most common nonferromagnesian member of the mica family is muscovite. Mica minerals are silicate minerals and muscovite is recognized for its transparent to silvery appearance.

Silicate of Silicon and Oxygen

Quartz is the only common silicate mineral made entirely of silicon and oxygen. It is a major component of many rocks and is known for its hard and glassy nature.

High-Temperature Silicate Based on Color

Olivine is a high-temperature silicate, often named for its greenish color. This mineral can form during the cooling and crystallization of magma.

Silicate with Striations

Feldspar, particularly plagioclase feldspar, is characterized by striations on its surfaces. The striations are fine grooves that are visible on cleavage surfaces.

Chemical Weathering Product

Clay minerals, such as kaolinite, often originate from the chemical weathering of silicate minerals. These minerals are known for their fine particle size and soft texture.

Key concepts

Amphibole Group

The Amphibole Group is an intriguing family of silicate minerals often known for their complex crystal structure. They are watchetiscilicate crystals and are quite distinct due to their elongated form. A common member of this group is hornblende.
Hornblende is typically black or dark green and is found in igneous and metamorphic rocks. It gets its distinctive color from the presence of ions like magnesium, iron, and calcium.
Key features:

• Pleochroic, meaning their color changes when viewed from different angles.
• Two cleavage planes at intersecting angles of 120 and 60 degrees.

These characteristics make hornblende a valuable mineral for geological studies.

Mica Family

The Mica Family consists of sheet silicate minerals known for their perfect basal cleavage. Muscovite is a prominent nonferromagnesian member of this family. This means it doesn't have iron or magnesium in its composition, which gives it a light, silvery, or sometimes colorless appearance.
Muscovite is notably flexible and can be split into thin sheets, making it valuable in certain industrial applications.
Advantages of muscovite:

• High heat resistance.
• Excellent electrical insulation.

Apart from muscovite, the mica family includes other minerals like biotite, which contrasts muscovite with its darker tones.

Chemical Weathering

Chemical Weathering is a natural process that involves the alteration of rock minerals due to chemical reactions with atmospheric and biological substances. One of its key products is clay minerals such as kaolinite.
This process happens when minerals like feldspar in rock react with water, carbon dioxide, or organic acids and eventually decompose. As these reactions occur, they result in the formation of softer and finer minerals.
Characteristics of chemical weathering effects:

• Leads to soil formation essential for plant growth.
• Helps in the cycling of minerals and elements in the environment.

Understanding these changes is crucial for geologists to comprehend earth's surface processes and soil chemistry.

Silicon and Oxygen

Silicon and Oxygen form the backbone of the Earth’s crust, with quartz being the prime example. Quartz is a ubiquitous mineral composed entirely of these two elements, forming a pattern of interlocking tetrahedra.
It is renowned for its hardness and resistance to weathering, thus retaining its presence in many rock types, including granite and sandstone.
Uses of quartz:

• Used in glassmaking and electronics due to its hardness and transparency.
• In jewelry and watches because of its durability and aesthetic appeal.

The pure composition of quartz underscores its importance in geological processes and highlights its versatility in human applications.

High-Temperature Silicate

High-Temperature Silicates are minerals that crystallize from hot molten materials. Olivine is a classic high-temperature silicate, often recognized by its greenish coloration, bestowed by magnesium and iron. It crystallizes at high temperatures found in igneous rock formations.
Olivine is found in the mantle of the Earth and also in basaltic lava, suggesting a deep origin. This mineral is studied to understand more about mantle composition and magmatic processes.
Notable properties:

• Transparent to translucent appearance when pure.
• High melting point, indicating robustness.

Olivine plays a significant role in the study of geology due to its occurrence in significant geological formations.

Striations on Minerals

Striations on Minerals are tiny parallel lines or grooves on crystal surfaces, often resulting from the growth process or cleavage properties. Plagioclase feldspar, a widespread silicate mineral, is renowned for its striations.
These striations are formed due to the presence of twin crystal structures and serve as useful identifiers for mineralogists.
Importance of striations:

• Helps in differentiating feldspar minerals from others.
• Assists in understanding crystal growth patterns.

Studying striations can reveal the geological history and environmental conditions during the mineral’s formation.