This lesson is about minerals, building blocks of rocks . The following lessons are mostly about rocks. Nearly all rocks are made of minerals. Therefore, to be ready to learn about rocks, you must first understand what minerals are as well as the characteristics of some of the most common minerals.

In the lesson, you are introduced to some basic principles of chemistry (this is for those of you who have not had a chemistry course). This will help you understand material covered in the chapters on rocks, weathering, and the composition of Earth's crust and its interior. You will discover that each mineral is composed of specific chemical elements, the atoms of which are in a remarkably orderly arrangement. A mineral's chemistry and the architecture of its internal structure determine the physical properties used to distinguish it from other minerals. You should learn how to readily determine physical properties and use them to identify common minerals.

Questions

What is a mineral?

What is a rock?

What are the physical properties of minerals?

What is the crytaline structure?

How many groups of minerals accoring to the chemical composition?

Define the different groups of mineral? Give examples for each group?

How do mineral form?

What is the luster of mineral?

What is the streak of mineral?

What is the cleavage of mineral?

What is the fracture of mineral?

Where do sediments come from?

What are three types of rocks?

Extra readings

1. Rocks are naturally formed, consolidated material composed of grains of one or more minerals. Minerals are crystalline (orderly three-dimensional arrangements of atoms).

2. Elements are substances that cannot be broken down by ordinary chemical methods. Atoms are the smallest particles of elements. They are constructed of protons, neutrons (forming the nucleus) and electrons. Atomic mass number, atomic number and atomic weight control the"character" of an element, particularly its isotopes.

3. Chemical activity is related to ions and their bonding.

4. Eight elements comprise 98% of the weight of the crust. Oxygen accounts for half the weight of the crust. Silicon is the second most abundant element in the crust and silicate minerals, combinations of oxygen and silicon, are the most common in the crust.

5. Crystalline substances have a three-dimensional, regularly repeating, orderly pattern of their anions. The silica tetrahedron is the basic"building block" of most common (silicate) minerals. Silicate structure reflects the arrangement of silica tetrahedra and the numbers of shared oxygens. These structures include: isolated silicate structure (no shared oxygens), chain-silicates (two shared oxygens), sheet silicates (three shared oxygens), and framework silicates (four shared oxygens).

6. Minerals are naturally occurring solids that are crystalline (which is to say that it has a periodically repeating arrangement of atoms) and have a specific chemical composition. Specific chemical composition reflects the orderly internal arrangement of atoms. Zoning further reflects the orderly arrangement.

7. A small number of rock-forming minerals comprise most of the crust. Five mineral groups (feldspar, quartz, pyroxene, amphibole, and mica) account for greater than 90% of the earth's crust. Feldspars are the most common crustal mineral, while olivine is the most abundant mineral in the earth as a whole. Nonsilicates are either native elements or are classified by their negative ion. These include ore minerals of commercial value.

8. Physical properties are used to identify minerals. These include color, streak, luster, hardness, external crystal form, cleavage, fracture, specific gravity, special properties (smell, taste, striations, magnetism), and other properties (double refraction, effects of polarized light, x-ray defraction). Chemical tests can be used to identify minerals.

Technical terms

amphibole group

Mineral group in which all members are double chain silicates.

atom

Smallest possible particle of an element that retains the properties of that element.

atomic mass number

The total number of neutrons and protons in an atom.

atomic number

The total number of protons in an atom.

atomic weight

The sum of the weight of the subatomic particles in an average atom of an element, given in atomic mass units.

biotite

Iron/magnesium bearing mica.

bonding

Attachment of an atom to one or more adjacent atoms.

calcite

Mineral with the formula CaCO3.

chain silicate structure

Silicate structure in which two of each tetrahedron's oxygen ions are shared with adjacent tetrahedrons, resulting in a chain of tetrahedrons.

clay mineral group

Collective term for several clay minerals.

cleavage

The ability of a mineral to break along preferred planes.

covalent bonding

Bonding due to the sharing of electrons by adjacent atoms.

crystal form

Arrangement of various faces on a crystal in a definite geometric relationship to one another.

crystalline

Describing a substance in which the atoms are arranged in a regular, repeating, orderly pattern.

density

Weight per given volume of a substance.

earthy luster

A luster giving a substance the appearance of unglazed pottery.

electron

A single, negative electric charge that contributes virtually no mass to an atom.

element

A substance that cannot be broken down to other substances by ordinary chemical methods. Each atom of an element possesses the same number of protons.

feldspar group

Group of most common minerals of Earth’s crust. All feldspars contain silicon, aluminum, and oxygen and may contain potassium, calcium, and sodium.

ferromagnesian mineral

Iron/magnesium-bearing mineral, such as augite, hornblende, olivine, or biotite.

fracture

The way a substance breaks where not controlled by cleavage.

framework silicate structure

Crystal structure in which all four oxygen ions of a silica tetrahedron are shared by adjacent ions.

glassy (vitreous) luster

A luster that gives a substance a glazed, porcelainlike appearance.

hardness

The relative ease or difficulty with which a smooth surface of a mineral can be scratched; commonly measured by Mohs’ scale.

ion

An electrically charged atom or group of atoms.

ionic bonding

Bonding due to the attraction between positively charged ions and negatively charged ions.

isolated silicate structure

Silicate minerals that are structured so that none of the oxygen atoms are shared by silica tetrahedrons.

isotope

Atoms (of the same element) that have different numbers of neutrons but the same number of protons.

luster

The quality and intensity of light reflected from the surface of a mineral.

magnetite

iron oxide that is attracted to a magnet.

metallic luster

Luster giving a substance the appearance of being made of metal.

mica group

Group of minerals with a sheet silicate structure.

mineral

A naturally occurring, crystalline solid that has a specific chemical composition.

Mohs’ hardness scale

Scale on which ten minerals are designated as standards of hardness.

muscovite

Transparent or white mica that lacks iron and magnesium.

neutron

A subatomic particle that contributes mass to an atom and is electrically neutral.

nonmetallic luster

Luster that gives a substance the appearance of being made of something other than metal (e.g., glassy).

nucleus

Protons and neutrons form the nucleus of an atom. Although the nucleus occupies an extremely tiny fraction of the volume of the entire atom, practically all the mass of the atom is concentrated in the nucleus.

olivine

A ferromagnesian mineral with the formula (Fe, Mg)₂SiO₄.

ore mineral

A mineral of commercial value.

plagioclase feldspar

A feldspar containing sodium and/or calcium in addition to aluminum, silicon, and oxygen.

potassium (orthoclase) feldspar

A feldspar with the formula KAlSi₃O₈.

proton

A subatomic particle that contributes mass and a single positive electrical charge to an atom.

pyroxene group

Mineral group, all members of which are single chain silicates.

quartz

Mineral with the formula SiO₂.

sheet silicate structure

Crystal structure in which each silica tetrahedron shares three oxygen ions.

silica

A term used for oxygen plus silicon.

silicates

A substance that contains silica as part of its chemical formula.

silicon-oxygen tetrahedron

Four-sided, pyramidal object that visually represents the four oxygen atoms surrounding a silicon atom; the basic building block of silicate minerals. Also called a silica tetrahedron or a silicon tetrahedron.

specific gravity

The ratio of the mass of a substance to the mass of an equal volume of water, determined at a specified temperature.

streak

Color of a pulverized substance; a useful property for mineral identification.

striations

On minerals, extremely straight, parallel lines.