NATURALLY OCCURRING The Chemistry of Color...
Transcript of NATURALLY OCCURRING The Chemistry of Color...
Chemistry of Color
1
The Chemistry of Color
Why do minerals
have different colors?
Characteristics of Minerals
NATURALLY OCCURRING
SOLID
INORGANIC
SPECIFIC CHEMICAL COMPOSITION
SPECIFIC ATOMIC ARRANGEMENT
Mineral Properties
Predictable physical properties
Controlled by chemical composition
and/or structure
Mineral Properties
Color
Streak: Color of powdered mineral
Luster: Character of reflected light
Cleavage/Fracture: Mineral breakage form
Habit: Mineral growth form
Hardness: Resistance to scratching
Specific Gravity (Density)
Miscellaneous Properties: e.g., smell, magnetism
Chemistry of Color
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Aspects of Light
Amplitude (height of wave) corresponds to the intensity (brightness) of light
Wavelength corresponds to the energy of light
In the visible spectrum wavelength corresponds to color
Wavelength of Light
Visible light is only a
tiny, moderate energy
fraction of the
electromagnetic
spectrum
Longer wavelengths
(e.g., radio waves)
have less energy
Shorter wavelengths
have more energy
Absorption Results in Color(A Familiar Example from Biology)
What Color?
What is the color of a mineral that absorbs
green and yellow light?
What spectral colors are absorbed by a
yellow mineral?
Chemistry of Color
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Absorption and Emission of Light Color and Compositon
Certain elements are strong pigmenting
agents
Produce strong color when they are
present in either crystal lattice or impurity.
Called chromophores.
Color and Compositon
Chromium (Cr): orange, green
Cobalt (Co): pink, purple, blue
Copper (Cu): blue, green
Iron (Fe): red, green, yellow
Manganese (Mn): pink
Transition Metals
Chemistry of Color
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Color vs Streak
If mineral color due to major constituent…
color and streak similar
If mineral color due to trace constituent (ppm)
streak will be pale or white