Minerals

1
Minerals

• Chapter 2 in Review book,
• Chapter 4 in textbook

2
What is a mineral?

• Minerals are naturally occurring, solid,
  inorganic compounds or elements.
• Earths crust made up of about 3000 minerals.
• Display crystalline structure which means that
  the atoms are arranged in a regular pattern which
  is repeated.

3
How to identify

• Geologists rely on several simple tests to
  identify minerals.
• These are based on the minerals physical and
  chemical properties.
• Usually best to use a variety of tests to
  determine a minerals name rather than rely on
  just one.

4
Crystal Form

• Some minerals are immediately recognizable by
  their crystal shape.
• Halite (common salt) always occurs in perfect
  cubes.
• Quartz has double pointed ends and is six-sided .
• Careful, because crystal might be miss formed.

5
Luster

• The way a mineral reflects light from its
  surface.
• Metallic-shiny surfaces which reflect light, kind
  of like a chrome bumper on a car.
• Non-metallic luster might be described as dull,
  pearly, waxy, silky or earthy.

6
Hardness

• Hardness is the measure of how easily a mineral
  can be scratched.
• One of the most reliable tests for identifying a
  mineral.
• Uses a scale of ten minerals.

7
Cleavage and Fracture

• Atomic arrangement determines how a mineral will
  break.
• A mineral that splits easily and along flat
  planes is said to have cleavage.
• Minerals that break along rough or jagged edges
  are said to have fracture.

8
Streak

• Streak is the color of the mineral when it is
  broken and powdered.
• This test is done by dragging the mineral across
  an unglazed porcelain plate.

9
Streak

• Mineral must be softer than plate.
• Some metallic minerals will have different color
  streak than outside color-hematite.

10
Color

• One of the most noticeable characteristics.
• Some minerals can be a variety of colors
  (quartz).
• In general, color is the least reliable clues to
  a minerals identity.

11
Special properties

• Calcite-double vision, bubbles with acid.
• Magnetite-magnetic.
• Flourite-glows under a black light.
• Sulfur-bad smell.
• Talc-greasy feel.

12
Texture/ density

• Describes how a mineral feels to the touch.
• Smooth, rough, ragged, greasy or soapy.
• Density can be used to describe various minerals
  (galena).