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