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Questions and Answers
What is the primary textural classification of diorite?
What is the primary textural classification of diorite?
- Crystalline
- Medium to coarse-grained (correct)
- Fine-grained
- Porphyritic
Which mineral is NOT commonly found in gabbro?
Which mineral is NOT commonly found in gabbro?
- Olivine
- Anorthite
- Quartz (correct)
- Hornblende
What relationship do the constituents of syenite exhibit?
What relationship do the constituents of syenite exhibit?
- Porphyritic
- Graphic
- Inter-grown
- All of the above (correct)
In what stage of igneous activity does syenite typically occur?
In what stage of igneous activity does syenite typically occur?
What type of rock is dolerite classified as?
What type of rock is dolerite classified as?
What makes andesite suitable for use as a decorative building stone?
What makes andesite suitable for use as a decorative building stone?
Which of the following is a chief constituent of gabbro?
Which of the following is a chief constituent of gabbro?
What is a predominant feature of the mineralogical composition of dolerite?
What is a predominant feature of the mineralogical composition of dolerite?
What is the primary focus of petrology?
What is the primary focus of petrology?
Which statement best describes a rock?
Which statement best describes a rock?
What distinguishes a mineraloid from a mineral?
What distinguishes a mineraloid from a mineral?
Which is NOT a characteristic of a mineral?
Which is NOT a characteristic of a mineral?
What kind of materials can be categorized as organic?
What kind of materials can be categorized as organic?
What is the significance of studying petrology in engineering?
What is the significance of studying petrology in engineering?
Which of the following is considered a defining characteristic of all minerals?
Which of the following is considered a defining characteristic of all minerals?
Which of the following best describes mineraloids?
Which of the following best describes mineraloids?
Which igneous rocks are considered most suitable for construction due to their high crushing strength?
Which igneous rocks are considered most suitable for construction due to their high crushing strength?
For what type of structures are basalts recommended?
For what type of structures are basalts recommended?
What characteristic defines lamprophyres in terms of their texture?
What characteristic defines lamprophyres in terms of their texture?
Where do lamprophyres typically occur?
Where do lamprophyres typically occur?
Which mineral is NOT typically found in granite?
Which mineral is NOT typically found in granite?
What texture can granite exhibit?
What texture can granite exhibit?
What type of rock do peridotites typically replace in construction due to their appearance?
What type of rock do peridotites typically replace in construction due to their appearance?
What is a common feature of peridotites regarding their occurrence?
What is a common feature of peridotites regarding their occurrence?
What contributes to the colour variation in granites?
What contributes to the colour variation in granites?
Which minerals are commonly extracted from peridotites?
Which minerals are commonly extracted from peridotites?
Which of the following statements about diorite is true?
Which of the following statements about diorite is true?
Which igneous rocks can provide information about the Earth's mantle compositions?
Which igneous rocks can provide information about the Earth's mantle compositions?
What is a characteristic feature of diorite's texture?
What is a characteristic feature of diorite's texture?
What is the primary process through which igneous rocks are formed?
What is the primary process through which igneous rocks are formed?
Which type of igneous rock is formed from magma that cools and crystallizes within the Earth's crust?
Which type of igneous rock is formed from magma that cools and crystallizes within the Earth's crust?
What characteristic texture do igneous rocks typically have?
What characteristic texture do igneous rocks typically have?
Extrusive igneous rocks are formed from magma that becomes what before solidification?
Extrusive igneous rocks are formed from magma that becomes what before solidification?
Which of the following is an example of intrusive igneous rock?
Which of the following is an example of intrusive igneous rock?
How does the rate of cooling affect the texture of igneous rocks?
How does the rate of cooling affect the texture of igneous rocks?
What distinguishes an intrusive igneous rock from an extrusive one?
What distinguishes an intrusive igneous rock from an extrusive one?
What happens to magma during the formation of extrusive igneous rocks?
What happens to magma during the formation of extrusive igneous rocks?
Which of these correctly categorizes igneous rocks based on mode of occurrence?
Which of these correctly categorizes igneous rocks based on mode of occurrence?
Which characteristic is true for extrusive igneous rocks?
Which characteristic is true for extrusive igneous rocks?
Study Notes
Igneous Rocks Overview
- Igneous rocks are formed from the cooling and solidification of molten material, or magma.
- Classified into two categories: intrusive (formed underground) and extrusive (formed above ground).
- Commonly used in construction due to high strength, particularly granites, syenites, and dolerites.
Diorite
- Generally coarse- to medium-grained with an inequigranular texture.
- Characterized by a holocrystalline arrangement of minerals, predominantly plagioclase feldspar.
- Quartz is usually absent but may be present as quartz-diorite.
- Used in construction and as decorative stones.
Syenite
- Displays coarse- to medium-grained and holocrystalline textures.
- Can show a graphic or porphyritic relationship among mineral constituents.
- Typically forms when magma cools during the plutonic stage of igneous activity.
- Applied in construction and mineral extraction of nephaline.
Andesite
- Abundant volcanic rock, second in prevalence to basalts.
- Occurs as crystallized lava flows; ideal for decorative construction stone and paint industry.
Gabbro and Dolerite
- Gabbro is a plutonic basic rock rich in plagioclase feldspars like labradorite and anorthite, along with mafic minerals (augite, hornblende).
- Dolerite is a hypabyssal volcanic rock, primarily made of calcic plagioclase and dark minerals such as augite and olivine.
Petrology
- Branch of geology focusing on rock formation, classification, and occurrence.
- Rock is defined as naturally occurring solid aggregates of minerals, mineraloids, or organic material.
Mineralogical Definitions
- Mineral: Naturally occurring inorganic substance with a defined internal structure and chemical composition.
- Mineraloid: Solid that resembles a mineral but lacks ordered atomic structure; may have indefinite chemical composition.
- Organic Material: Remains of living organisms included in geological contexts.
Igneous Rock Textures
- Intrusive igneous rocks have coarse textures due to slower cooling rates within the Earth.
- Extrusive rocks cool quickly, resulting in fine-grained textures and interlocking crystalline structures.
Economic Importance
- Many igneous rocks, such as peridotites and pegmatites, contain valuable minerals offering economic benefits.
- Correct selection of igneous rocks is crucial for construction purposes, such as for tunnels, foundations, and structural work.
Characteristics of Specific Igneous Rocks
- Granite: Composed mainly of quartz and feldspar. Shows diverse colors based on feldspar type.
- Lamprophyre: Coarse-grained, forms in existing igneous/metamorphic rock fissures.
- Peridotite: Typically coarse-grained, found in sills and dykes, valued for its mineral content.
Applications
- Andesite and syenite are used in construction as decorative stones.
- Gabbro is utilized for its strength in structural applications.
Occurrence Overview
- Igneous rocks can occur as surface flows or intrusions, affecting their texture and mineral composition.
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Description
Test your knowledge on the textures of igneous rocks such as diorite and syenite. Explore different arrangements and grain sizes of mineral grains as you answer this quiz. Improve your understanding of holocrystalline and ineguigranular textures!