Physical Properties of Minerals: Physical Properties of Minerals **The physical properties of a mineral are a DIRECT result of the INTERNAL ARRANGMENT OF ATOMS.**
Some properties are more useful then others to determine what a mineral is.
However rarely is one physical property enough to identify a mineral.
The following are the main physical properties used to identify minerals Color: Color Color is the LEAST useful physical property
It is the least useful for two reasons:
More than one mineral can be a certain color
2 Samples of the same mineral can have different colors!
Slide3: Each of these minerals has a different color yet all are QUARTZ Slide4: Both of these minerals are green, however the one on the
left is Olivine, and the one on the right is Malachite
These are examples of why color is the WORST identifying characteristic. Streak: Streak 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 colored streak regardless of the color of the sample Luster: Luster The way in which a mineral reflects light is its luster.
There are two types of luster:
Minerals shiny like polished metal.
Don’t shine like polished metal, and are sometimes described as glassy, pearly, dull and earthy. Metallic Luster: Metallic Luster Two Examples: Nonmetallic Luster: Nonmetallic Luster A few Examples: Hardness: Hardness Hardness is a measure of a minerals resistance to being scratched.
This is one of the KEY means of identifying a mineral
It also determines how quickly a mineral is broken up by weathering.
The hardness of a mineral is tested using Moh’s Hardness scale, a penny, your finger nail, a glass plate, and a nail. Moh’s Hardness Scale: Moh’s Hardness Scale Cleavage: Cleavage 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.
Cleavage is caused when weak bonds in a mineral are split apart. Cleavage in One Direction: Cleavage in One Direction The classic example of cleavage in one direction is Mica.
The mineral breaks in to flat sheets. Cleavage in 2 Directions: Cleavage in 2 Directions Orthoclase is the classic example of cleavage in 2 directions.
Cleavage in three Directions: Cleavage in three Directions Halite is the classic example of cleavage in 3 directions at right angles
It breaks into cube shaped pieces. Fracture: Fracture Some minerals do not break along nice flat planar surfaces.
This type of breakage is called fracture. Special Properties:: Special Properties: Some minerals display properties that no other minerals display.
These traits are:
bubbling in acid
double refraction of light or polarization
(creates 2 images from 1)
A mineral may magnify an image below it.
Powdered form may bubble in acid