Minerals of the Earth’s CrustCHAPTER 1 SECTION 1

HISTORY OF THE EARTH IN 10 MINUTES

Origins of Mineralogy?

• Thought to have been founded by Georgius Agricola (1556)• Advanced by Romé de l’Isle, a French scientist who proposed

the concept of the unit cell (or crystal)• A repeating 3 dimensional pattern composed of atoms or

compounds, which make up the mineral

For example, halite (table salt) is composed of tightly-packed sodium (Na) and chlorine (Cl) atoms arranged in a definite pattern

What are minerals?

• Inorganic solids that are naturally formed over time• What is the difference between minerals and rocks?

• Rocks are made up of a combination of different minerals, but minerals have a definite and repeating chemical structure

Four questions for determining a mineral

1. Is it a solid?2. Is it nonliving material?3. Does it have crystalline structure?4. Is it formed in nature?

• Minerals are usually made up of chemical compounds• i.e., halite – NaCl, hematite – Fe2O3

• However, there are minerals that only consist of one type of atom

• We call these native elements• i.e., sulfur (S), gold (Au), silver (Ag)

Two Groups of Minerals

1. Silicate Minerals• must contain silicon (Si) & oxygen (O)• make up more than 90% of Earth’s crust• usually combine with other elements such as aluminum (Al), iron (Fe),

magnesium (Mg) and potassium (K)

2. Nonsilicates• Do not contain a combination of Si & O• Instead, usually contain atoms or combinations of atoms of carbon (C),

Oxygen, fluorine (F), sulfur (S)

• Most important classes of nonsilicates• Native elements

• Copper (Cu), Silver (Ag),gold (Au), sulfur (S)• Carbonates

• Contain combination of C & O• i.e., CaCO3 (chalkboard chalk)

• Halides• When F, Cl, B or I combine with Na, K or Ca

• Used in the chemical industry and to make detergents

…Nonsilicates (cont’d)• Oxides

• Occur when elements like aluminum (Al) and iron (Fe) chemically combine with O

• Sulfates• Contain S and O

• Sulfides• Contain one or more elements such as lead (Pb), iron (Fe) or nickel

(Ni)• Used to make batteries and electronic parts • Two Advances Point Toward a Cheaper Electric-Car Battery

Identifying Minerals (Ch.1 Section 2)

• Just as we can identify different foods by tasting, seeing or smelling them, we can identify minerals based on known properties each possess

• Color, luster, cleavage, fracture, hardness, and density are the most common basic properties used in science classes

• Scientists now use different forms of technology to quickly determine the chemical composition of each mineral.

• The principal difference between it and the biological microscope is the presence of two polarizing elements, one above and one below the stage, in the petrographic microscope. These elements and a number of other accessories are employed to observe and measure a great many optical properties of minerals, which in turn can be used to identify the minerals and even obtain approximate compositional information.

• http://www.uwosh.edu/faculty_staff/wenner/optical/Lab%201-Intro%20to%20%20microscope.htm

Petrographic or “P” microscope

Identifying Minerals (Ch.1 Section 2)P microscope images• Other methods include X-ray diffraction and the electron

microscope• Both produce images of substances at the atomic level that

help to identify minerals and indicate chemical composition Color• Color is probably the first property you will notice when identifying

minerals.• However, it should only be used as a quick reference so you can

recall different minerals that have similar appearances. (We work from general to specific)• Deductive reasoning

• Some minerals can take on different appearances from spending time in different environments

Luster• The way the surface reflects light (shiny / dull)• Metallic (very shiny)• Submetallic (eh)• Nonmetallic (dull)• See Fig 1. on p. 8 in your textbook

Streak• Color of a mineral in powder form• color of the streak is not always the same as the color of the

mineral sample• Rubbing the mineral on a porcelain plate (streak plate), will

produce a streak of the mineral• Because the streak (powder form) of the mineral is unaffected by

air / weather the streak is more reliable than color of the mineral alone.

Cleavage and Fracture

• Cleavage • the tendency of some minerals to break along smooth, flat

surfaces• Fracture • The tendency of minerals to break unevenly along curved or

irregular surfaces

cleavagefracture

Hardness

• A mineral’s resistance to being scratched• Moh’s hardness scale• Freidrich Mohs – determined a minerals identity could be

determined by comparing the mineral with several minerals of known hardness

• There are 10 reference minerals that we will be learning about

1. Talc2. Gypsum3. Calcite4. Fluorite5. Apatite

6. Orthoclase7. Quartz8. Topaz9. Corundum10. Diamond

Density

• You tell me what density is…

Special Properties• Fluorescence• Magnetism• Chemical reaction• Taste

Question

• If a mineral scratches calcite but is scratched by apatite, what is the mineral’s hardness?• 4

• What might be a good way to memorize the hardness scale for future reference?• T, G, C, F, A, O, Q, T, C, D

• Describe each of the identification techniques

The Formation, Mining, and Use of Minerals (Ch.1.3)

Mining

• Methods for mining• Surface mining• Sub-surface mining• Both are used to extract ore from underground depending

on the ore’s depth• Ore – mineral deposit large enough and pure enough to

be mined for profit

Surface mining

• Used to remove minerals on or close to the surface of the Earth• Open pit mining, surface coal mines and quarries• Surface Mining

Sub-surface mining

• Used to extract minerals that are too deep to be surface mined• Drift mine, slope mine, shaft mine• Siberian diamond mine

Responsible Mining

• Miners must adhere to strict regulations set by the EPA to ensure mining does not compromise the integrity of the ecosystem surrounding the mine

• Often waste must be chemically treated before it leaves the mine so it cannot contaminate the water table• EPA regulations

Mine Reclamation• Returning the mine back its original condition after mining has

been completed• As a society, we can reduce our demand for minerals by

following the RRR mentality• Reduce• Reuse• Recycle

The Use of Minerals

• Metallic Minerals (light cannot pass through)• Good for conducting heat, electricity • Can be pounded into different shapes• Very strong when combined with other elements and treated

physically or chemically• Malleable, ductile

• Nonmetallic (may allow light to pass through)• Good insulators of electricity• Used very widely in industry• i.e., Calcite is used in concrete

Gemstones

• Diamond, ruby, sapphire, emerald• Typically mined due to their value as precious and semi-

precious gems• Jewelry• Must be durable; able to be cut and shaped into the desired

product