Minerals

1
Minerals

• Chapter 5

2
Characteristics of Minerals

• Natural, inorganic solid with definite chemical
  composition, orderly internal structure, and
  characteristic set of physical properties

3
Ask 4 Questions

• Is it inorganic?
• Does it occur naturally?
• Is it solid in crystalline form?
• Does it have a consistent chemical composition?

4
Kinds of Minerals

• 3,000 , but only 20 common
• Rock-forming minerals
• 10 make up 90 of crust
• Quartz, orthoclase, plagioclase, muscovite,
  biotite, calcite, dolomite, halite, gypsum,
  ferromagnesian minerals
• 2 main groups silicates and nonsilicates

5
Silicates

• Combo of Si and O
• Feldspars are most common
• Si O metal
• Orthoclase K
• Plagioclase Na, Ca, both
• Quartz
• Ferromagnesians (olivines, pyroxenes, amphiboles,
  biotite)
• 96 of Earths crust

6
Nonsilicates

• 4 of Earths crust
• No Si and O
• 6 major groups
• Carbonates
• Halides
• Native elements
• Oxides
• Sulfates
• sulfides

7
Identifying Minerals

• Section 5.2

8
Identifying Minerals

• Mineralogists
• Specific properties due to chemical composition
  and crystalline structure
• Some properties can be seen while others must be
  tested

9
Color

• Usually not very reliable because minerals are
  similar in color or some minerals contain small
  amounts of elements that change the color
• Example corundum is usually colorless unless it
  contains chromium, which turns it into a ruby
• When corundum has cobalt and titanium, it is
  sapphire
• Amethyst is quartz (usually colorless) with
  manganese and iron

10
Color

• Also unreliable because of weathering
• Example iron pyrite turns from gold to black
• When examining, use freshly exposed surfaces

11
Streak

• Color in powdered form
• Metallics usually dark streak
• Nonmetallics usually light streak or streak of
  their standard color
• If mineral is harder than streak plate, there
  will be no streak.

12
Luster

• Light reflected from a minerals surface
• Metallic
• Nonmetallic
• Glassy
• Waxy
• Pearly
• Brilliant
• Dull or earthy

13
Cleavage

• Tendency of a mineral to split along specific
  planes of weakness to form smooth, flat surfaces

http//geology.csupomona.edu/alert/mineral/cleavag
e.htm
14
Fracture

• Break unevenly into curved or irregular surfaces
• Uneven or irregular (rough surface)
• Splintery or fibrous
• conchoidal

http//geology.csupomona.edu/alert/mineral/cleavag
e.htm
15
Hardness

• Mohs Hardness Scale

16
Crystal Shape

• Determined by temperature and pressure

17
Density

• Ratio of mass to volume
• Depends on the kinds of atoms and how closely
  atoms are packed
• Minerals common in Earths crust are usually 2-3
  g/cm3

18
Special Properties

• Flourescence
• Calcite glows red in UV light
• Phosphorescence
• When mineral continues to glow after UV has been
  removed
• Chatoyancy and Asterism
• Results from closely packed parallel fibers
• Cats eye

19
Special Properties

• Double Refraction
• Calcite splits light into two parts and produces
  a double image
• Magnetism
• Nonsilicates that contain iron (magnetite, i.e.
  lodestone)
• Radioactivity
• Unstable nuclei decay into more stable nuclei by
  releasing particles and energy
• Geiger counter
• Pitchblende contains U

20
(No Transcript)