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Questions and Answers
What is the chemical composition of quartz?
Why is quartz classified in the silicate group despite not having a characteristic SiO4 4 – chemical group?
Which type of rocks is quartz an essential mineral in?
What is the most common appearance of quartz?
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In which type of rocks can quartz be recognized by its variable shape, absence of cleavage, and conchoidal fracture?
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What percentage of the Earth's crust does quartz constitute by volume?
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Where are high-grade coal deposits found in India?
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Which region in India is known for lignite coal deposits?
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Where are petroleum deposits primarily found in India?
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Which sedimentary formations in India are potential sources of petroleum?
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Where are fresh petroleum reserves located off in India?
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Which valleys are expected to have deep-seated deposits of petroleum?
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What happens when a drop of cold 10% dilute hydrochloric acid is applied to calcite?
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Which property of a mineral does tenacity measure?
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What are taste and magnetic properties diagnostic of in some minerals?
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Why do some minerals never occur together in nature?
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In mineral identification, why is it unnecessary to determine all properties of a specimen?
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If a mineral exhibits metallic lustre, three cleavages at right angles, grey color, and black streak, what is it likely to be?
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What is the color of biotite, a ferromagnesian mica?
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Which mineral has a vitreous luster that is pearly on cleavage?
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In which rocks is biotite commonly found?
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What is the main reason muscovite is focused on among non-ferromagnesian phyllosilicates?
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What is the internal structure of muscovite composed of?
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Which mineral is the stable form of calcium carbonate?
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What is the specific gravity of low specific gravity minerals?
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How is specific gravity measured in a laboratory?
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What is the importance of crystal habit in mineral identification?
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Which minerals fall under the category of high specific gravity minerals?
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How is transparency defined in relation to a crystal?
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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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Description
Explore the chemical composition, physical properties, natural environments, and technical uses of quartz, a common rock-forming mineral. Learn about its classification and unique characteristics.
