Chapter 2: Matter and Minerals

Mineralogy

the branch of geology that deals with the identification and classification of minerals

Mineral

any naturally occurring inorganic solid that possesses an orderly crystalline structure and a definite chemical composition that allows for some variation.

Naturally Occurring

A characteristic of a mineral: must form through natural geologic processes.

Generally inorganic

A characteristic of a mineral: must not contain carbon matter.

Solid substance

Characteristic of minerals that means they are not liquids or gases within normal temperature ranges on Earth's surface.

Orderly Crystalline structure

A characteristic of a mineral: atoms (ions) are arranged in an orderly, repetitive manner.

Definite chemical composition that allows for some variation

A characteristic of a mineral: must be chemical compounds having compositions that can be expressed by a chemical formula.

Crystals

Regularly shaped objects

Rock

Any solid mass of mineral, or mineral-like, matter that occurs naturally as part of our planet.

Aggregate

minerals are joined in such a way that their individual properties are retained.

Atoms

all matter, including minerals, is composed of minute building blocks

Proton

a stable subatomic particle occurring in all atomic nuclei, with a positive electric charge

Neutron

an uncharged elementary particle that has a mass nearly equal to that of the proton

Electron

a stable subatomic particle with a charge of negative electricity, found in all atoms and acting as the primary carrier of electricity in solids.

Electrical charge

physical property of matter that causes it to experience a force when placed in an electromagnetic field. It can be positive or negative.

Principal shells

electrons show that they move about the nucleus in regions

Valence electrons

a single electron or one of two or more electrons in the outer shell of an atom that is responsible for the chemical properties of the atom

Atomic Number

The number of protons in the nucleus of an atom

Element

a group of the same kind of atoms

Periodic Table

Elements are organized so that those with similar properties line up in columns, referred to as groups.

Chemical compounds

Most elements join with atoms of other elements

Octet Rule

Atoms tend to gain, lose, or share electrons until they are surrounded by eight valence electrons

Chemical bond

a transfer or sharing of electrons that allows each atom to attain a full valence shell of electrons.

Ionic bond

one atom gives up one or more of its valence electrons to another atom to form ions. An attraction of oppositely charged ions to one another, producing an electrically neutral ionic compound.

Ions

positively and negatively charged atoms

Covalent bond

a chemical bond formed by the sharing of a pair of electrons between atoms

Metallic bond

When the valence electrons are shared among all the atoms in a substance,

Malleable

they can be hammered into thin sheets

Ductile

they can be drawn into thin wires

Optical Properties

a material's behavior when electromagnetic radiation (light) is incident on the material's surface

Luster

The appearance or quality of light reflected from the surface of a mineral

Metallic luster

Minerals that have the appearance of metals, regardless of color

Nonmetallic Luster

the luster of a mineral which reflects light from its surface but does not shine like a metal

Ability to transmit light

Ability of the mineral to be either opaque, translucent, or transparent

Color

it is considered a diagnostic property of only a few minerals.

Streak

The color of a mineral in powdered form

Crystal shape or habit

the common or characteristic shape of individual crystals or aggregates of crystals.

Mineral Strength

How easily minerals break or deform under stress

Hardness

a measure of the resistance of a mineral to abrasion or scratching.

Mohs Scale of Hardness

A numerical value of hardness which consists of 10 minerals arranged in order from 1 (softest) to 10 (hardest),

Cleavage

the tendency of a mineral to break (cleave) along planes of weak bonding.

Fracture

Appearance of a surface broken in directions other than along cleavage planes. Minerals that have chemical bonds that are equally, or nearly equally, strong in all directions

Tenacity

describes a mineral's resistance to breaking, bending, cutting, or other forms of deformation.

Sectile

materials that can be cut into thin shavings

Elastic

Materials that will bend and snap back to their original shape after stress is released.

Density

an important property of matter, is defined as mass per unit volume.

Specific Gravity

a number representing the ratio of a mineral's weight to the weight of an equal volume of water.

Double Refraction

on certain minerals where a light ray enters the crystal and splits up into two separate rays

Effervescence

Chemical reaction where small bubbles of gas escape from a liquid.

Rock-forming minerals

Minerals that make up most of the rocks of Earth's crust

Economic Minerals

Although less abundant, many other minerals are used extensively in the manufacture of products

oxygen (O), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg).

8 major elements in the crust

Silicates

silicon and oxygen are by far the most common elements in Earth's crust. Furthermore, these two elements readily combine to form the basic "building block" for the most common mineral group

Non-silicates

minerals that are not composed of silicate groups. These minerals may contain oxygen atoms but not in combination with silicon.

Silicate Minerals

those minerals that contain [SiO4]−4 as the fundamental unit of their chemistry and structure.

Silicon-oxygen tetrahedron

This structure consists of four oxygen atoms surrounding a much smaller silicon atom,

Olivine Group

Cleavage: none and silicate structure: single tetrahedra

Pyroxene Group (Augite)

Cleavage: two planes at 90 degrees and silicate structure: single chains

Amphibole Group (Hornblende)

Cleavage: two planes at 60 and 120 degrees and silicate structure: double chains

Mica (Biotite)

Cleavage: one plane and silicate structure: sheets (dark mineral)

Mica (Muscovite)

Cleavage: one plane and silicate structure: sheets (light mineral)

Potassium Feldspar (Orthoclase)

Cleavage: two planes at 90 degrees and silicate structure: 3D framework (K-rich mineral)

Plagioclase Feldspar

Cleavage: two planes at 90 degrees and silicate structure: 3D framework (Ca-Na rich mineral)

Quartz

Cleavage: none and silicate structure: 3D framework

Light Silicate Minerals

Generally light in color and having a specific gravity of about 2.7, contain varying amounts of aluminum, potassium, calcium, and sodium.

Feldspars

The most abundant mineral group. One group of these minerals contains potassium ions in its crystalline structure. The other group contains calcium and/or sodium ions

Quartz

a major constituent of many igneous, sedimentary, and metamorphic rocks. Found in a wide variety of colors (caused by impurities), quite hard (7 on the Mohs scale) and exhibits conchoidal fracture when broken

Clay Minerals

light silicates that typically form as products of chemical weathering of igneous rocks. They make up much of the surface material we call soil

Dark Silicate Minerals

contain iron and magnesium in their crystalline structures and high specific gravity, which is between 3.2 and 3.6, significantly greater than the specific gravity of the light silicate minerals.

Olivine Group

Abundant in Earth's upper mantle, black to olive green in color, has a glassy luster, and often forms small crystals which gives it a granular appearance

Pyroxene Group (Augite)

a group of dark silicate minerals that are important components of dark-colored igneous rocks. A black, opaque mineral with two directions of cleavage that meet at nearly 90-degree angles

Amphibole Group (Hornblende)

Usually dark green to black in color. Its cleavage angles are about 60 degrees and 120 degrees. Found in igneous rocks, which make up the dark portion of otherwise light-colored rocks.

Biotite

the dark, iron-rich member of the mica family and its shiny appearance helps distinguish it from other dark silicate minerals.

Garnet

Another dark silicate mineral and much like olivine, it has a glassy luster, lacks cleavage, and exhibits conchoidal fracture.

Non-silicate Minerals

minerals are typically divided into groups, based on the negatively charged ion or complex ion that the members have in common. Make up only about 8 percent of Earth's crust

Native Elements

made from just a single element, bonded to itself

Renewable Resources

can be replenished over relatively short time spans.

Non-renewable Resources

the processes that create them are so slow that significant deposits take millions of years to accumulate.

Mineral Resources

All discovered and undiscovered deposits of useful minerals that can be extracted now or at some time in the future.

Ore Deposit

a naturally occurring concentration of one or more metallic minerals that can be extracted economically.

Gemstones

a precious or semiprecious stone, especially one cut, polished, and used in a piece of jewelry.