Physical Properties

**Physical properties of a mineral are a
DIRECT result of the INTERNAL
ARRANGEMENT of ATOMS
Some properties are more useful than others to determine what a mineral is

Using only 1 physical property to identify a mineral is usually not enough
The following are the main physical properties used to identify minerals

Color is the LEAST useful physical property for 2 reasons:
1) More than one mineral can be a certain color
2) 2 samples of the same mineral can be 2 different colors!

Each of these minerals has a different color, yet they are all QUARTZ!
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Both of these minerals are green. However, one is Olivine, and one is Malachite.
This is another reason why color is the WORST way to identify a mineral
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Streak is the color of a mineral in powder form
The powder forms when the mineral is rubbed against a rough surface
An unglazed ceramic tile is used as the rough surface
Some minerals have a distinct streak color, however most leave a clear streak
This limits the usefulness of the test
However it is more reliable then color alone because each mineral leaves the same color streak even if the minerals are different color samples

Using a ceramic plate
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Luster: The way in which a mineral reflects light
2 Major Types of Luster
– 1) Metallic
• Shiny like polished metal
– 2) Nonmetallic
• Don’t shine like polished metal and can be described as glassy, pearly, dull/earthy and others

Two examples:
Galena and Pyrite
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A few examples: rose quartz, talc, olivine, augite
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Hardness is a measure of a mineral’s resistance to being scratched .
This is one of the KEY means of identifying a mineral.
It also determines how quickly a mineral is broken down by weathering.
The hardness of a mineral is tested using
Moh’s Hardness scale , a penny, your fingernail, a glass plate, and a nail.

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Cleavage is the tendency of a mineral to split along certain flat surfaces, or planes of cleavage.
Cleavage can occur in one or more planes.
Cleave is caused when weak bonds in a mineral are split apart.

Classic example of cleavage in 1 direction is Mica: breaks into flat sheets
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Classic example of cleavage in 2 directions is Orthoclase:
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Classic example of cleavage in 3 directions at right angles: Halite
It breaks into cubed shaped pieces
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Some minerals do not break along nice flan planar surfaces.
This type of breakage is called fracture
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Some minerals display properties that no other minerals display:
– Magnetism
– Bubbling in acid
– Powdered form bubbles in an acid
– Ability to magnify
– Double refraction of light or polarization
• (creates 2 images from one)