300minerals

MINERALS AND ROCKS

I. California K-6 Standards for Minerals and Rocks -

II. Mineral

III. Minerals that are Useful

IV. Silicate minerals

V. Abundant Silicate Minerals

VI. Rock

VII. Relationships Between the Rock Types

VIII. Possible essay questions

IX. Practice Questions

I. California K-6 Standards for Minerals and Rocks -

Grade 2

Earth Sciences Topics

3. Earth is made of materials that have distinct properties and provide resources for human activities. As the basis for understanding this concept, students know:

a. how to compare the physical properties of different kinds of rocks and that rocks are composed of different combinations of minerals.

Grade 3

Earth Science Topics

4. The properties of rocks and minerals reflect the processes that formed them. As a basis for understanding this concept, students know:

a. how to differentiate among igneous, sedimentary, and metamorphic rocks by their properties and methods of formation (the rock cycle).

b. how to identify common rock-forming minerals (including quartz, calcite, feldspar, mica, and hornblende) and ore minerals using a table of diagnostic properties.

II. Mineral -

Definition - A mineral:

Is naturally occurring
Is inorganic (non-living)
Is solid
Has a precise chemical composition (or variable within limits)
And has precise physical properties (or variable within limits)

Identification of minerals by their physical properties -

Crystal form - results from the way in which the molecules of a mineral pack together. Described by terms such as cubic, rhombic, hexagonal, tetragonal, etc.

Luster - results from the way in which light is reflected from the molecules of a mineral. Described by terms such as glassy, waxy, pearly, dull, etc. (example)

Hardness - results from the cohesion of the molecules in a mineral. Described by a numerical scale called Moh's hardness scale which ranges from 1 for the softest minerals to 10 for the hardest.

1. Talc

2. Gypsum

(fingernail ~2.5)

3. Calcite

(copper penny ~3.5)

4. Fluorite

5. Apatite

(knife ~5.5)

6. Feldspar

(glass ~6.5)

7. Quartz

8. Topaz

9. Corundum

10. Diamond

Color - results from the wavelengths of light that are reflected from the molecules of a mineral. Described by the name of the color seen.

Streak - results from the wavelengths of light that are reflected from the molecules of a mineral that is in a finely powdered form.

Cleavage - results from the way in which the molecules of a mineral pack together. Described by the number of constant directions in which the mineral breaks. (example)

Specific gravity (heft) - results from the atomic weight of the molecules in the mineral. Described as very heavy, heavy, moderate, light, and very light.

Other physical properties - magnetism, taste, odor, ductility, reaction to acid, radioactivity, and fluorescence. (example)

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III. Minerals that are useful to our present-day civilization

Elements Gold - our standard of trade
Copper - our major conductor of electricity
Diamond - the gemstone form of the element carbon
Graphite - used in "lead" pencils; another form of carbon
Sulfur - used in fertilizer, plastic, explosives, drugs, and insecticides
Oxides Hematite - chief ore of iron (iron and oxygen)
Limonite - secondary ore of iron (iron and oxygen)
Magnetite - secondary ore of iron (iron and oxygen)
Bauxite - chief ore of aluminum (aluminum and oxygen)
Sulfides Galena - chief ore of lead (lead and sulfur)
Pyrite - used in making sulfuric acid (iron and sulfur); commonly called "fool's gold"
Chalcopyrite - chief ore of copper (copper, iron, and sulfur)
Sphalerite - chief ore of zinc (zinc and sulfur)
Sulfates Gypsum - makes plaster (calcium, sulfur, and oxygen
Carbonates Calcite - makes cement (calcium, carbon, and oxygen)
Malachite - secondary ore of copper (copper, carbon, oxygen, and hydrogen)

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IV. Silicate minerals -

Because oxygen and silicon make up about 75% of the earth's crust, it follows that most of the minerals in the crust of the earth will contain oxygen and silicon ions.
The most common ionic pattern is for 4 oxygen ions to gather in a tetrahedral pyramid around a single silicon ion This arrangement is called the silicon tetrahedron.

Problem - calculate the electrical charge on the silicon tetrahedron -

Silicon, atomic number 14, is a cation. If it gives away the excess electrons in its outer energy level, what will be its positive charge?
Oxygen, atomic number 8, is an anion. If it takes in electrons to fill its outer energy level, what will be its negative charge?
Combine or add the negative charges on 4 oxygen ions and the positive charge on 1 silicon ion to get the total charge on the silicon tetrahedron.

Silicon tetrahedra are themselves arranged in various ways such as single and double chains and sheets to form many different minerals.

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V. Abundant silicate minerals that form most of the world's rocks -

Quartz - used in glass making and in radio electronics
Feldspar - world's most common mineral; used in ceramics Orthoclase - pink to white, not striated, 2 cleavages of 90° each
Plagioclase - white to gray, striated, 2 cleavages of 90° each
Mica - used as an insulator Muscovite - colorless, cleaves into elastic sheets
Biotite - black, cleaves into elastic sheets
Ferromagnesian Minerals Hornblende - black, 2 cleavages at 56° and124°
Augite - black, 2 cleavages at 90° each
Olivine - dark green to black, no cleavage
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VI. Rock -

A rock is an aggregate of one or more minerals. There are three basic kinds of rocks in the world.

Igneous rocks - rocks that are created when melted rock cools and solidifies by the process of crystallization.

Sedimentary rocks - rocks that are created when sediment, which forms during the weathering of other rocks, is deposited and later is compacted and/or cemented together into a solid by the process of lithification.

Metamorphic rocks - rocks that are created by squeezing and heating other rocks to high pressures and to temperatures that are high, but are below melting temperature. This process is called metamorphism.

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VII. Relationships between the three rock types -

Both igneous and sedimentary rocks must pass through a stage of metamorphism before they can get hot enough to melt, so all igneous rocks must originate from the melting of metamorphic rocks.
Sediment is produced by the weathering of igneous rocks, metamorphic rocks, or even pre-existing sedimentary rocks. Lithification produces sedimentary rocks from the sediment.
Metamorphic rocks are produced by the metamorphism (applying heat and pressure) of sedimentary rocks, igneous rocks, or even pre-existing metamorphic rocks.
All the above factors function simultaneously so as to continuously recycle the rocks of the earth in a rock cycle.

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VIII. Possible essay questions -

Give the definition of the word mineral.
Describe how minerals are identified by their physical properties.
Briefly explain how the minerals diamond and graphite are similar.
List three minerals that serve as ores of iron.
List three minerals that serve as ores of copper.
Briefly explain why silicate minerals are the most abundant minerals in the world.
List the eight most common rock-forming minerals.
Describe the origin of Sedimentary rocks.
Describe the origin of metamorphic rocks.
Describe in detail and illustrate the rock cycle.

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IX. Practice Questions

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