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Transcript of Minerals
is a solid
must occur in nature
has a definite chemical composition
has a crystal structure
must be inorganic (non-living)
Cleavage is the tendency to break along flat surfaces. The way a mineral breaks depends on how the atoms are bonded together. Weaker bonds display more cleavage (smoother when broken apart). If the broken surfaces are smooth then it is said to have perfect cleavage.
How do we identify minerals?
Color and Streak
Luster is the way in which light reflects from the surface. The two major types of luster are metallic and nonmetallic. A mineral with a nonmetallic luster can be shiny, but does not appear to be made of metal.
Some minerals are a different color when they are whole compared to when they are ground into a fine powder. A mineral's streak is the color of the powder when the mineral is scraped across a surface. The surface most commonly used is called a streak plate. Streak is a better clue than the surface color of what the mineral's identity is.
Fracture is the tendency of a mineral to break into irregular pieces. In a mineral that displays fracture, the bonds that join the atoms are fairly equal in strength, unlike when dealing with cleavage. The mineral doesn't break along flat surfaces because there aren't weak areas present.
A mineral's hardness is its resistance to being scratched. Harder minerals have stronger bonds between atoms. A hardr mineral will always scratch a softer one. To determine a mineral's hardness we use Mohs Scale of Hardness.
To use Mohs Scale of Hardness remember that a mineral can be scratched only by other minerals that have the same hardness or are harder.
Talc is the softest mineral (1). Diamond is the hardest mineral (10).
Your fingernail = 2.5
Penny = 3
Steel Nail = 6.5
Mohs Scale of Hardness
So....how do we identify minerals?
color and streak
A Helpful Pnuemonic...