Podcast
Questions and Answers
Which of the following factors can affect the color of a mineral?
Which of the following factors can affect the color of a mineral?
What is the purpose of determining the streak of a mineral?
What is the purpose of determining the streak of a mineral?
Which type of luster is characteristic of minerals such as pyrite and galena?
Which type of luster is characteristic of minerals such as pyrite and galena?
What can the crystal form of a mineral provide clues to?
What can the crystal form of a mineral provide clues to?
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Which type of cleavage is characteristic of minerals such as mica and graphite?
Which type of cleavage is characteristic of minerals such as mica and graphite?
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What is the unit of measurement for the Mohs hardness scale?
What is the unit of measurement for the Mohs hardness scale?
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Which of the following optical properties is the variation in color when viewed from different directions?
Which of the following optical properties is the variation in color when viewed from different directions?
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What is the purpose of determining the density of a mineral?
What is the purpose of determining the density of a mineral?
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Colour of galena
Colour of galena
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Match the following
Match the following
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Match the following
Match the following
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Which mineral on the Mohs scale just barely resists being scratched by a knife?
Which mineral on the Mohs scale just barely resists being scratched by a knife?
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A particular mineral scratches both fluorite and apatite but is scratched by corundum. Which mineral is it?
A particular mineral scratches both fluorite and apatite but is scratched by corundum. Which mineral is it?
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Which mineral has a hardness that can be determined using a window glass as a reference but not a penknife?
Which mineral has a hardness that can be determined using a window glass as a reference but not a penknife?
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Identify the mineral that is NOT scratched by a window glass.
Identify the mineral that is NOT scratched by a window glass.
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If a mineral leaves a scratch on orthoclase but is itself scratched by corundum, what might it be?
If a mineral leaves a scratch on orthoclase but is itself scratched by corundum, what might it be?
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Number of silicates in Mohs hardness scale
Number of silicates in Mohs hardness scale
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Match the following
Match the following
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Study Notes
Physical Properties of Minerals
Color
- Can be affected by impurities, defects, or chemical composition
- Some minerals have a distinctive color, while others may have a range of colors
- Examples: malachite (green), azurite (blue), cinnabar (red)
Streak
- The color of the powder produced when a mineral is scratched on a porcelain plate
- Can be different from the mineral's apparent color
- Useful for identifying minerals, especially those with a metallic luster
Luster
- The way light reflects off a mineral's surface
- Types of luster:
- Metallic (e.g., pyrite, galena)
- Vitreous (e.g., quartz, feldspar)
- Earthy (e.g., kaolinite, halite)
- Pearly (e.g., opal, moonstone)
- Resinous (e.g., amber, sulfur)
Crystal Form
- The external shape of a mineral crystal
- Can provide clues to a mineral's internal structure
- Examples: cubic (e.g., halite, galena), octahedral (e.g., magnetite, spinel), tabular (e.g., mica, biotite)
Cleavage
- The way a mineral breaks along flat surfaces
- Depends on the mineral's internal structure and bonding
- Types of cleavage:
- Basal cleavage (e.g., mica, graphite)
- Prismatic cleavage (e.g., amphibole, pyroxene)
- Pinacoidal cleavage (e.g., orthoclase, microcline)
Hardness
- A mineral's resistance to scratching
- Measured on the Mohs hardness scale (1-10)
- Examples: soft minerals (talc, gypsum), medium-hard minerals (calcite, fluorite), hard minerals (quartz, topaz)
Density
- A mineral's mass per unit volume
- Can be used to distinguish between minerals with similar properties
- Examples: high-density minerals (galena, hematite), low-density minerals (halite, selenite)
Optical Properties
- Refractive index: the degree to which a mineral bends light
- Birefringence: the difference between a mineral's refractive indices in different directions
- Pleochroism: the variation in color when viewed from different directions
Physical Properties of Minerals
Color
- Impurities, defects, or chemical composition can affect a mineral's color
- Some minerals have a distinctive color, while others have a range of colors
- Examples of minerals with distinct colors: malachite (green), azurite (blue), cinnabar (red)
Streak
- The color of the powder produced when a mineral is scratched on a porcelain plate
- Streak can be different from the mineral's apparent color
- Useful for identifying minerals, especially those with a metallic luster
Luster
- The way light reflects off a mineral's surface
- Types of luster include:
- Metallic (e.g., pyrite, galena)
- Vitreous (e.g., quartz, feldspar)
- Earthy (e.g., kaolinite, halite)
- Pearly (e.g., opal, moonstone)
- Resinous (e.g., amber, sulfur)
Crystal Form
- The external shape of a mineral crystal
- Can provide clues to a mineral's internal structure
- Examples of crystal forms: cubic (e.g., halite, galena), octahedral (e.g., magnetite, spinel), tabular (e.g., mica, biotite)
Cleavage
- The way a mineral breaks along flat surfaces
- Depends on the mineral's internal structure and bonding
- Types of cleavage include:
- Basal cleavage (e.g., mica, graphite)
- Prismatic cleavage (e.g., amphibole, pyroxene)
- Pinacoidal cleavage (e.g., orthoclase, microcline)
Hardness
- A mineral's resistance to scratching
- Measured on the Mohs hardness scale (1-10)
- Examples of minerals by hardness: soft (talc, gypsum), medium-hard (calcite, fluorite), hard (quartz, topaz)
Density
- A mineral's mass per unit volume
- Can be used to distinguish between minerals with similar properties
- Examples of minerals by density: high-density (galena, hematite), low-density (halite, selenite)
Optical Properties
- Refractive index: the degree to which a mineral bends light
- Birefringence: the difference between a mineral's refractive indices in different directions
- Pleochroism: the variation in color when viewed from different directions
Principles of Minerals
- The Mohs scale of hardness is used to determine the numerical value of a mineral's hardness.
- The Mohs scale consists of 10 minerals arranged in order of increasing hardness.
- The minerals on the Mohs scale are:
- Talc Silicate (hardness 1)
- Gypsum Sulfate (hardness 2)
- Calcite Carbonate (hardness 3)
- Fluorite Fluride Chalcide (hardness 4)
- Apatite Phosphate (hardness 5)
- Orthoclase Silicate (hardness 6)
- Quartz Silicate (hardness 7)
- Topaz Silicate (hardness 8)
- Corundum Oxide (hardness 9)
- Diamond C (hardness 10)
Determining Hardness without Testing
- In the absence of hardness testing, certain materials can be used to determine approximate hardness.
- A finger nail can scratch up to about 2.5, meaning it can scratch minerals up to but not including Calcite.
- A window glass can scratch up to about 5, meaning it can scratch minerals up to but not including Feldspar.
- A penknife can scratch up to about 5.
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Description
Learn about the physical properties of minerals, including color, streak, and luster. Understand how these properties can be used to identify minerals and their composition.
