Question

Each of the following statements describes one or more characteristics of a particular metamorphic rock. For each statement, identify the metamorphic rock that is being described: a. calcite rich and nonfoliated b. loosely coherent and composed of broken fragments that formed along a fault zone c. represents a grade of metamorphism between slate and schist d. composed of tiny chlorite and mica grains and displaying excellent rock cleavage e. foliated and composed predominantly of platy materials f. composed of alternating bands of light and dark silicate minerals g. hard and nonfoliated, often produced by contact metamorphism

Short answer

a. Marble, b. Fault breccia, c. Phyllite, d. Slate, e. Schist, f. Gneiss, g. Quartzite.

Step-by-step solution

Identify a metamorphic rock that is calcite rich and nonfoliated

The metamorphic rock that is calcite-rich and nonfoliated is marble. Marble forms from limestone and has a crystalline structure due to recrystallization of calcite during the metamorphic process.

Identify a metamorphic rock that is loosely coherent and found along fault zones

Fault breccia is the metamorphic rock characterized by being loosely coherent and composed of broken fragments, which result from rock being broken and ground together along a fault zone.

Identify a metamorphic rock between slate and schist

Phyllite is the metamorphic rock that represents a grade of metamorphism between slate and schist. It has a fine-grained texture with a slight sheen caused by tiny micas.

Identify a metamorphic rock composed of tiny chlorite and mica grains

The metamorphic rock described is slate. Slate is fine-grained, composed of minerals such as chlorite and mica, and is well known for its excellent rock cleavage.

Identify a foliated metamorphic rock with platy materials

Schist is a foliated metamorphic rock predominantly composed of platy materials, such as micas, giving it a pronounced schistosity or foliation.

Identify a metamorphic rock with alternating bands of minerals

Gneiss is the metamorphic rock that has alternating bands of light and dark silicate minerals, often giving it a characteristic banded appearance.

Identify a hard, nonfoliated rock produced by contact metamorphism

Quartzite is a hard, nonfoliated metamorphic rock that forms from quartz sandstone, typically due to the process of contact metamorphism.

Key concepts

Marble

Marble is a fascinating metamorphic rock, well-known for its beauty and alluring patterns. Originating from limestone, marble undergoes a metamorphic process where the calcite in the limestone recrystallizes, forming a denser rock with an interlocking crystal structure. This transformation gives marble its distinct nonfoliated texture.
One of the key characteristics of marble is its richness in calcite. The rock is predominantly made up of calcium carbonate, a component that contributes to its dazzling whiteness, although it can appear in various colors due to mineral impurities. Marble's aesthetic appeal is one reason why it's commonly used in sculptures and building materials.
Another important aspect of marble is its relatively soft nature compared to other stones, which allows it to be polished to a high sheen, revealing its intricate patterns and varying hues. This makes marble highly sought after for decorative applications.

Fault Breccia

Fault breccia is quite unique in the realm of metamorphic rocks. It forms in fault zones where rocks are subjected to intense pressure and fracturing. This rock is known for its loosely coherent texture, which is essentially an assemblage of broken fragments cemented together.
The formation process of fault breccia involves a mechanism known as cataclasis, where intense pressure due to faulting causes rocks to grind against each other, resulting in angular fragments. These fragments are then bound together by a fine-grained matrix, typically consisting of crushed rock or minerals.
The nature of fault breccia, with its chaotic appearance and diverse composition, can provide valuable insights into the history and dynamics of fault zones. It's important to note that fault breccia is not as commonly used in construction or decoration due to its brittleness and less cohesive nature.

Phyllite

Phyllite is an intermediate-grade metamorphic rock, bridging the gap between slate and schist in the metamorphic timeline. It is distinguished by its fine-grained texture and silky luster, which results from the abundance of tiny mica flakes that catch and reflect light.
Phyllite forms under conditions of moderate heat and pressure, causing the minerals, such as muscovite and chlorite, to increase in size from the smaller slate particles. This gives phyllite its characteristic sheen, often described as having a "phyllitic luster."
The rock cleavage of phyllite is another notable feature, as it cleaves into thin, wavy sheets, which sets it apart from slate's more planar cleavage. Due to its aesthetic appeal and structural properties, phyllite is often used in construction for decorative aggregates and as facing stone.

Slate

Slate is best known for its exceptional rock cleavage, which makes it ideal for roofing, flooring, and many other applications. It is a fine-grained metamorphic rock, formed from shale through low-grade metamorphism.
This rock primarily consists of minerals such as chlorite, mica, and quartz. These minerals impart slate with its smooth, even layers that split tidily into thin sheets. This characteristic splitting is a result of the alignment of platy minerals under directed pressure, enhancing its use in tiles and educational blackboards.
Besides its practicality, slate often comes in a variety of colors, ranging from grey and black to green or red, depending on its mineral content. Slate is not just functional but also adds a touch of elegance to architectural designs.

Schist

Schist is a foliated metamorphic rock packed with platy minerals, primarily micas, giving it a pronounced foliation known as schistosity. It forms under higher temperatures and pressures than phyllite, leading to larger mineral grains and more distinct foliation patterns.
The schist formation process involves recrystallization, where minerals grow and restructure to form an interleaved imbued matrix. As such, schist often contains garnet, staurolite, and quartz, which together with mica, create its characteristic sheen and texture.
The pronounced layers of schist not only mark its foliation but also contribute to its ability to split into slabs. As a result, it’s frequently used in construction, making it useful for decorative stone and as a component in aggregates. The vibrant patterns in schist also make it a visually appealing rock specimen.

Gneiss

Gneiss is renowned for its banded and foliated appearance, a result of alternating layers of light and dark mineral composition. This eye-catching structure is created by high-grade metamorphism that aligns minerals like quartz and feldspar distinctively.
As gneiss forms, it undergoes intense heat and pressure, leading to the segregation of mineral bands. The light bands are usually made up of quartz and feldspar, while the dark bands consist of biotite or amphibole, giving gneiss its signature striped look.
Gneiss is quite durable and can withstand weathering, which makes it a popular choice in both outdoor and indoor construction. It is particularly favored for countertops, flooring, and decorative paving due to its stunning appearance and robustness.

Quartzite

Quartzite is a durable metamorphic rock originating from quartz sandstone. Through contact metamorphism, quartz sandstone's grains become tightly fused, creating a hard, nonfoliated rock.
This transformative process enhances quartzite's strength and makes it resistant to weathering, which is why it’s commonly used in high-wear applications like road construction and railway ballast. Quartzite's tight mineral bonds give it a granular texture and a sugary appearance. Colors in quartzite typically range from white to gray; however, the presence of iron oxide can produce pink shades. Its hardness, comparable to granite, and beautiful finish also make quartzite a popular material for countertops and decorative stones.
Overall, quartzite's natural beauty combined with its impressive durability has made it a favored material in both practical and aesthetic applications.