Introduction to Rocks and Petrology

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Questions and Answers

What is the primary factor used to classify rocks into igneous, sedimentary, and metamorphic types?

Age of the rock

Origin of formation (correct)

Mineral hardness

Physical characteristics

Which term refers to the science that studies the mineral composition and origin of rocks?

Mineralogy

Sedimentology

Petrology (correct)

Geology

Which type of rock is formed from the solidification of magma or lava?

Igneous rock (correct)

Sedimentary rock

Volcanic rock

Metamorphic rock

What process transforms fragmented materials into sedimentary rocks?

Compaction Signup and view all the answers

Which of the following is an example of an intrusive igneous rock?

Granite Signup and view all the answers

What type of sedimentary rock is formed from chemical processes?

Halite Signup and view all the answers

Which characteristics are most significant in the classification of igneous rocks?

Mineral composition and texture Signup and view all the answers

The term 'detrital rocks' refers to which kind of rocks?

Sedimentary rocks Signup and view all the answers

What is the primary texture characteristic of extrusive igneous rocks?

Smooth and fine grains Signup and view all the answers

Which type of igneous rock forms from magma that cools slowly at great depths?

Gabbro Signup and view all the answers

What is the primary characteristic of metamorphic rocks?

They undergo a change of form due to PVT change. Signup and view all the answers

What distinguishes dynamic metamorphism from thermal metamorphism?

Dynamic metamorphism primarily occurs due to pressure, while thermal occurs due to heat. Signup and view all the answers

What is the process called when rocks are altered chemically and recrystallized?

Thermal metamorphism Signup and view all the answers

Which of the following metamorphic rocks is typically formed from shale?

Slate Signup and view all the answers

What is 'foliation' in metamorphic rocks?

An arrangement of minerals into bands or layers. Signup and view all the answers

Which type of metamorphism occurs due to high temperatures from magma or lava?

Contact metamorphism Signup and view all the answers

During which stage of the rock cycle do metamorphic rocks form?

Under conditions of high pressure and temperature. Signup and view all the answers

Which process allows metamorphic rocks to contribute to the formation of sedimentary rocks?

Weathering and erosion Signup and view all the answers

What type of metamorphism is primarily caused by tectonic forces?

Regional metamorphism Signup and view all the answers

What is banding in metamorphic rocks?

An arrangement of minerals in alternating layers. Signup and view all the answers

Which characteristic of minerals describes the external shape determined by the internal arrangement of molecules?

External crystal form Signup and view all the answers

What is defined as the property of a mineral breaking along specific planes?

Cleavage Signup and view all the answers

What color is malachite known for?

Green Signup and view all the answers

How many elements primarily compose about 98% of the earth's crust?

8 Signup and view all the answers

When does a mineral exhibit an irregular break without specific planes?

When it has a complex internal molecular arrangement Signup and view all the answers

Which of the following mineral groups are commonly occurring minerals in the earth's crust?

Major rock-forming minerals Signup and view all the answers

What does the lustre of a mineral refer to?

Its shining quality Signup and view all the answers

Which physical characteristic of a mineral is described by its ability to resist scratching?

Hardness Signup and view all the answers

What is the primary source of all minerals in the earth?

Hot magma Signup and view all the answers

In which mineral form does silicon typically combine with oxygen in the earth's crust?

Silicates Signup and view all the answers

What is the hardness of quartz on the Mohs scale?

7 Signup and view all the answers

Which of the following minerals has the lowest hardness on the Mohs scale?

Talc Signup and view all the answers

Which of the following is considered a ferrous metal?

Iron Signup and view all the answers

What characteristic differentiates opaque minerals from translucent minerals?

Ability to let light pass through Signup and view all the answers

Which of the following minerals can be classified as a precious metal?

Gold Signup and view all the answers

Which mineral gives a white streak despite being purple or green in color?

Fluorite Signup and view all the answers

Which type of rock is primarily associated with the formation of metallic minerals?

Igneous rocks Signup and view all the answers

What does the term 'streak' refer to in mineralogy?

The color of the powder produced when a mineral is scratched Signup and view all the answers

Which of the following describes non-metallic minerals?

They are devoid of malleability and ductility. Signup and view all the answers

Which mineral is ranked directly above corundum on the Mohs hardness scale?

Topaz Signup and view all the answers

Study Notes

What is Rock?

Rock is the solid mineral material forming the surface of the earth.
Rocks are composed of one or more minerals.
Petrology is the science of all things related to rocks, including composition, structure, texture, origin, occurrence, alteration, and relationships with other rocks.
The age of a rock is determined based on carbon-14 dating.

Rock Classifications

Rocks are classified into three types: Igneous, Sedimentary, and Metamorphic.

Igneous Rocks

"Ignis" is Latin for "fire."
Igneous rocks are formed from magma and lava from the earth's interior.
Igneous rocks are formed when magma cools and solidifies.
There are two types of igneous rocks:
- Intrusive rocks are formed when magma cools within the Earth's crust.
- Extrusive rocks are formed when lava cools on the Earth´s surface.
Igneous rocks are also classified based on the texture, size, and arrangement of grains.
- Slow cooling at depth results in large mineral grains.
- Sudden cooling at the surface results in small, smooth grains.
Examples of igneous rocks: Pegmatite, gabbro, granite, basalt, tuff

Sedimentary Rocks

Sedimentary rocks are also called detrital rocks.
The word "sedimentary" is derived from the Latin word "sedimentum," which means "settling."
Sedimentary rocks are formed from rock fragments that have been weathered, transported, and deposited.
The process of turning deposited sediments into rock is called lithification.
Sedimentary rocks occupy only 5% of the Earth's surface.
Sedimentary rocks are layered or stratified.
Three types of sedimentary rocks based on their formation:
- Mechanically formed sedimentary rocks (e.g., conglomerate, loess, limestone, sandstone)
- Chemically formed sedimentary rocks (e.g., potash, halite)
- Organically formed sedimentary rocks (e.g., chalk, coal, limestone, geyserites)

Metamorphic Rocks

The word "metamorphic" means "change of form."
Metamorphic rocks are formed when existing rocks are transformed by pressure, volume, and temperature changes.
Metamorphism is the process of recrystallization and reorganization of materials within existing rocks.
Igneous and metamorphic rocks together account for 95% of the Earth's crust.
Two types of metamorphism:
- Dynamic metamorphism: Breaking and crushing of minerals within rocks with no significant chemical changes.
- Thermal metamorphism: Chemical alteration and recrystallization of rock materials.
  - Contact metamorphism: Rocks come in contact with hot magma or lava.
  - Regional metamorphism: Recrystallization due to tectonic shearing, high temperature, or pressure.
Foliation, a layered appearance, is common in metamorphic rocks.
Banded rocks are a type of metamorphic rock where minerals form alternating layers in light and dark shades.
Examples of metamorphic rocks: Slate, diamond, marble, quartzite, schist, gneiss.

The Rock Cycle

The rock cycle is a continuous process where old rocks are transformed into new ones.
Igneous rocks are primary rocks, and sedimentary and metamorphic rocks are derived from them.
Igneous and metamorphic rocks can break into fragments that form sedimentary rocks.
Crustal rocks can be carried down into the Earth's mantle through subduction, melt, and turn into magma, which is the source of igneous rocks.
The rock cycle is a continuous process.

Minerals

98% of the Earth's crust is composed of eight elements: oxygen, sodium, calcium, iron, magnesium, silicon, aluminum, and potassium.
The remaining 2% of the crust is made up of titanium, hydrogen, phosphorus, manganese, carbon, sulfur, nickel, and other elements.
These elements combine to form minerals, which are naturally occurring, inorganic substances with a definite composition and physical properties.
About 2000 minerals have been found in the Earth's crust, but most are related to six major rock-forming minerals.
The hot magma in the Earth's interior is the source of all minerals.

Physical Characteristics of Minerals

External crystal forms: Determined by the internal arrangement of molecules (e.g., cubic, tetrahedral, tabular, hexagonal)
Cleavage: The property of breaking along specific planes (due to weaker bonding between atoms along some planes.)
Fracture: Breaking in an irregular manner when the internal molecular arrangement is complex.
Lustre: The shining quality of a mineral (metallic, glossy, silky, etc.)
Color: Depends on molecular structure, but impurities can affect color (e.g., quartz can be red, white, green)
Streak: The color of the mineral's powder.
Specific gravity: The ratio of a mineral's weight to the weight of an equal amount of water.
Hardness: A mineral's ability to resist scratching, measured by the Mohs Hardness Scale. The Mohs Scale uses 10 minerals with increasing hardness, from talc (1) to diamond (10).
Structure: Arrangement of individual crystals.
Transparency: Whether light passes through (transparent), passes through but is diffused (translucent), or doesn't pass through (opaque).

Mineral Classifications:

Metallic Minerals: Composed of metals.
- Precious metals: Platinum, gold, silver
- Ferrous metals: Iron mixed with other metals
- Non-ferrous metals: Metals other than iron (e.g., copper, aluminum, lead, zinc, tin)
Non-Metallic Minerals: Composed of non-metals (e.g., sulfur, silicon, phosphorus). Cement is a mixture of non-metallic minerals.

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Description

Explore the fundamental concepts of rocks, their classifications, and formations in this quiz. Learn about igneous, sedimentary, and metamorphic rocks, and the science of petrology that studies their characteristics. Test your knowledge on rock types and their origins.