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. Plagioclase feldspar, f. Kaolinite.

Step-by-step solution

Identify the most common amphibole mineral

The most common member of the amphibole group is Hornblende. It contains calcium, magnesium, iron, and other cations in its structure.

Determine the mica family member without iron or magnesium

Muscovite is the most common nonferromagnesian member of the mica family. It is a potassium aluminum silicate and lacks iron and magnesium.

Find the silicate mineral made only of silicon and oxygen

Quartz is the only common silicate mineral composed entirely of silicon and oxygen, represented by the chemical formula SiO₂.

Identify the high-temperature silicate named for its color

Olivine is a high-temperature silicate named for its olive-green color. It consists mainly of iron and magnesium silicate.

Recognize the striated silicate mineral

Plagioclase feldspar is known for having striations on its surface, which are fine parallel lines.

Determine the mineral from chemical weathering

Kaolinite is a clay mineral that forms as a product of the chemical weathering of silicate minerals. It consists of layered silicate sheets.

Key concepts

Amphibole Group

The amphibole group of minerals is fascinating due to its complexity and diverse composition. These minerals are primarily known for their elongated, prism-like structures. Hornblende, the most common amphibole, exemplifies this group with its dark color and shiny appearance. This mineral is rich in calcium, magnesium, iron, and other cations, which contribute to its dense nature and distinctive hardness. Amphiboles are typically found in metamorphic rocks, forming under conditions of high pressure and temperature. This makes them important indicators of the geological environment and processes.

Mica Family

The mica family is well-known for its sheet-like crystal structure that allows it to be split into thin, flexible layers. Muscovite, for example, is the most commonly occurring nonferromagnesian mica mineral. It is a potassium aluminum silicate with a pearly shine and color that ranges from clear to silver. Unlike other types of mica, muscovite does not contain iron or magnesium, making it lightweight and resistant to heat and electricity. This has made it useful historically in many industries, including electrical components and even early windows.

Silicon and Oxygen Silicates

Silicon and oxygen silicates form the cornerstone of Earth’s crust, with quartz being the most prevalent mineral in this category. Quartz is distinguished by its pure composition of silicon dioxide ( SiO₂ ), which contributes to its hardness and resistance to weathering. It can appear in a variety of colors, from clear, smoky, pink, or even purple, depending on the presence of minor impurities. The structure of quartz is a three-dimensional framework of silicate tetrahedra, which explains its stability and abundance in sedimentary, igneous, and metamorphic rocks.

High-temperature Silicates

High-temperature silicates, like olivine, play a critical role in understanding geological processes such as the formation of the Earth's mantle. Olivine is recognized by its olive-green color and notably high melting point. It primarily consists of iron and magnesium silicates, aligning it closely with ferromagnesian minerals. The presence of olivine in rocks indicates a high-temperature genesis, typically associated with mantle-derived volcanic rocks. Its relative instability at surface conditions also makes olivine an excellent marker for geological changes over time.

Chemical Weathering

Chemical weathering significantly alters the landscape by transforming silicate minerals into new substances, such as clay minerals. Kaolinite is a prime example, forming as a result of the breakdown of feldspar minerals under moist, acidic conditions. This transformation involves complex interactions with water and carbon dioxide from the atmosphere. Over time, the original silicate minerals dissolve and recompose into soft, white clay, making kaolinite abundant in soils, particularly in warm and humid climates. The process not only enriches the soil with nutrients but also helps in the long-term carbon cycle by sequestering carbon dioxide.