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Questions and Answers
What is the chemical composition of quartz?
What is the chemical composition of quartz?
- SiO4
- SiO
- SiO3
- SiO2 (correct)
Why is quartz classified in the silicate group despite not having a characteristic SiO4 4 – chemical group?
Why is quartz classified in the silicate group despite not having a characteristic SiO4 4 – chemical group?
- Due to its color
- Because of its typical tetrahedral structure (correct)
- Due to its density
- Because of its cleavage
Which type of rocks is quartz an essential mineral in?
Which type of rocks is quartz an essential mineral in?
- Plutonic rocks (correct)
- Sedimentary rocks
- Volcanic rocks
- Metamorphic rocks
What is the most common appearance of quartz?
What is the most common appearance of quartz?
In which type of rocks can quartz be recognized by its variable shape, absence of cleavage, and conchoidal fracture?
In which type of rocks can quartz be recognized by its variable shape, absence of cleavage, and conchoidal fracture?
What percentage of the Earth's crust does quartz constitute by volume?
What percentage of the Earth's crust does quartz constitute by volume?
Where are high-grade coal deposits found in India?
Where are high-grade coal deposits found in India?
Which region in India is known for lignite coal deposits?
Which region in India is known for lignite coal deposits?
Where are petroleum deposits primarily found in India?
Where are petroleum deposits primarily found in India?
Which sedimentary formations in India are potential sources of petroleum?
Which sedimentary formations in India are potential sources of petroleum?
Where are fresh petroleum reserves located off in India?
Where are fresh petroleum reserves located off in India?
Which valleys are expected to have deep-seated deposits of petroleum?
Which valleys are expected to have deep-seated deposits of petroleum?
What happens when a drop of cold 10% dilute hydrochloric acid is applied to calcite?
What happens when a drop of cold 10% dilute hydrochloric acid is applied to calcite?
Which property of a mineral does tenacity measure?
Which property of a mineral does tenacity measure?
What are taste and magnetic properties diagnostic of in some minerals?
What are taste and magnetic properties diagnostic of in some minerals?
Why do some minerals never occur together in nature?
Why do some minerals never occur together in nature?
In mineral identification, why is it unnecessary to determine all properties of a specimen?
In mineral identification, why is it unnecessary to determine all properties of a specimen?
If a mineral exhibits metallic lustre, three cleavages at right angles, grey color, and black streak, what is it likely to be?
If a mineral exhibits metallic lustre, three cleavages at right angles, grey color, and black streak, what is it likely to be?
What is the color of biotite, a ferromagnesian mica?
What is the color of biotite, a ferromagnesian mica?
Which mineral has a vitreous luster that is pearly on cleavage?
Which mineral has a vitreous luster that is pearly on cleavage?
In which rocks is biotite commonly found?
In which rocks is biotite commonly found?
What is the main reason muscovite is focused on among non-ferromagnesian phyllosilicates?
What is the main reason muscovite is focused on among non-ferromagnesian phyllosilicates?
What is the internal structure of muscovite composed of?
What is the internal structure of muscovite composed of?
Which mineral is the stable form of calcium carbonate?
Which mineral is the stable form of calcium carbonate?
What is the specific gravity of low specific gravity minerals?
What is the specific gravity of low specific gravity minerals?
How is specific gravity measured in a laboratory?
How is specific gravity measured in a laboratory?
What is the importance of crystal habit in mineral identification?
What is the importance of crystal habit in mineral identification?
Which minerals fall under the category of high specific gravity minerals?
Which minerals fall under the category of high specific gravity minerals?
How is transparency defined in relation to a crystal?
How is transparency defined in relation to a crystal?
Why is the Walker Balance apparatus useful in measuring specific gravity?
Why is the Walker Balance apparatus useful in measuring specific gravity?
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Study Notes
Crystal Habit
- Crystal habit refers to the external shape of a mineral
- It is used to identify minerals, as different environments can produce different crystal habits
Specific Gravity
- Specific gravity (sp.gr.) is the ratio of a mineral's weight in air to its weight in water
- It is measured using a steelyard apparatus like the Walker Balance
- In the field, specific gravity is estimated as low, medium, or high
- Low specific gravity minerals include silicates, carbonates, sulphates, and halides (sp.gr. 2.2-4.0)
- Medium specific gravity minerals include metallic ores like sulphides and oxides (sp.gr. 4.5-7.5)
- High specific gravity minerals include native metallic elements like copper, gold, and silver
Transparency
- Transparency is a measure of how clearly an object can be seen through a crystal
- Different degrees of transparency are described in Table 2.4
Reaction with Acid
- A drop of cold 10% dilute hydrochloric acid can produce reactions in certain minerals
- In calcite (CaCO3), bubbles of carbon dioxide form and make the acid froth
- In some sulphide ores, hydrogen sulphide is produced
Tenacity
- Tenacity is a measure of how a mineral deforms when it is crushed or bent
- Terms used to describe tenacity are given in Table 2.5
Rock Forming Minerals
- Quartz: SiO2, a major mineral in crystalline and detrital rocks
- Variable shape, no cleavage, conchoidal fracture, transparent gray in color
- Hardness of 7 on the Mohs scale, density of 2.65 · 103 kg/m3
- Biotite: K(Mg, Fe)3(AlSi3O10)(OH)2, a ferromagnesian mica
- Black or smoky brown in color, vitreous luster, pearly on cleavage
- Hardness ranges from 2.5 to 3, density from 2.8 · 103 kg/m3 to 3.2 ·103 kg/m3
- Muscovite: KAl2(AlSi3O10)(OH)2, an aluminous mica
- Occurs as sheets with pseudo-hexagonal faces
- Hardness is low, between 2 and 2.5; density ranges from 2.76 · 103 kg/m3 to 2.88 · 103 kg/m3
- Calcite: CaCO3, the stable form of calcium carbonate
- Found in sedimentary formations in parts of Assam, Tripura, and Manipur
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