Post on 31-Mar-2015
transcript
Properties of Minerals
Geologists use characteristics to tell
one mineral from another
What is a Mineral?
1. Must be a solid.
2. Must occur in nature.
3. Must have a definable chemical composition (NaCl).
4. Must have a crystalline structure.
5. Must be inorganic.• Video: http://www.youtube.com/watch?v=rTXSwnkieZc
Mineral Properties we will mainly study:
Luster Hardness
Cleavage Streak
Special Properties
• Fluorescence• Optical Properties: double
refraction• Taste• Conductivity• Reaction to Acid• Magnetism• Density
• Video: http://www.youtube.com/watch?v=cjA2-MrWAVU
• Song: http://www.youtube.com/watch?v=Sv_ApO7xiv8
Luster• Refers to the way light reflects from
the surface of the mineral. • There are two types of luster,
–Metallic: looks like polished metal. –Nonmetallic: does not look like
polished metal. • Nonmetallic can be shiny or dull.
Pyrite has metallic luster
Quartz has nonmetallic luster
Hardness
• Is measured by how easy it is to scratch.
• • Geologists use
Mohs Hardness Scale
Gypsum is soft, it can be scratched by a fingernail.
Calcite is soft, but a little harder because it cannot be
scratched by a fingernail, but it can be scratched by a penny.
Fluorite is harder. It can be scratched by a nail, but not a
penny or fingernail.
Diamonds are the hardest mineral, so it scratches every
mineral.
Cleavage• Not all minerals have cleavage. • Some minerals split easily along a
flat surface. • The number of lines that are created
when a mineral is split will be the number of cleavage lines.
Mica has cleavage in one direction.
It breaks along one line.
Feldspar has two lines of cleavage. It breaks along
two lines.
Streak• Red chalk on a chalk board makes
red marks. White chalk makes white marks.
• Not all minerals work this way. When some minerals are scratched along a ceramic streak plate, it creates a different color.
Gold• When gold is
run across a streak plate it makes a yellowish-gold color.
• That makes sense.
Pyrite or “Fool’s Gold”• When pyrite is run
across a streak plate, it has a black or dark green streak.
• Pyrite is not worth much money, while gold is worth a lot. They look alike, so miners call it fool’s gold.
Hematite• Hematite’s color is
grey, but its streak is red.
• Hema means blood.
• The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate.
One mineral property we will
not use…
COLOR
A mineral can be many different colors. Below is Mica.
Many minerals can be the same color. Below are gold colored minerals. Which one
is gold?
The answer…None of them
were real gold.
Just like with people…
Outside color does not tell you much about the
important characteristics.
Videos:
Mineral Identification
http://www.youtube.com/watch?v=VnM8ebB06MU
Hardness Scale
http://www.youtube.com/watch?v=7piTh8mH9zw