Geol 101 - Ch 3. Patterns in Nature: Minerals

Mineralogy

the study of minerals and their characteristics

What is a mineral?

1. Naturally occurring

2. Inorganic

3. Definable Chemical Composition

4. Crystalline material

5. Formed by geologic process

What is Crystalline Material?

Atoms resided in an orderly, fixed pattern, locked in place by chemical bonds.

What is a crystal structure?

arrangement of atoms/ions that define a pattern.

What is a definable chemical composition?

Possible to write a chemical formula for a mineral.

Inorganic vs Organic

Organic materials consist of carbon-carbon/carbon-hydrogen bonds and are formed in living organisms.

What is glass?

Solid in which atoms are not arranged in an orderly pattern.

What is a crystal?

A single continuous piece of crystalline solid that grows naturally.

What is a polymorph?

Two minerals that have the same chemical composition but a different crystal lattice structure.

How are minerals formed?

1. Solidification

2. Precipitation

3. Biomineralization

4. Solid-State Diffusion

5. Precipitation Directly from a Gas

What is the first step in forming a crystal?

A formation of a seed, or an extremely small crystal.

What is the second step in forming a crystal?

The crystal grows whereas the crystal faces move outward with the same orientation.

What is the third step in forming a crystal?

The youngest crystal forms overedge.

How are crystals formed by solidification?

Atoms attach the seed when the melt becomes cool enough that thermal vibrations can no longer break apart the attraction between the seed and the atoms.

How are crystals formed by precipitation?

The solution becomes saturated; dissolved ions per unit volume of solution become so great that they can get close enough to each other to bond together.

How are shape dimensions defined?

Dimensions of the crystal and the angles between the faces.

How do new minerals grow?

They grow to fill the space that is available.

What are anhedral grains?

Minerals w/o well-formed crystal faces.

What are euhedral crystal?

Unimpeded mineral growth that displays well formed crystal faces.

What is a geode?

Mineral-lined cavity in rock; may be euhedral

How can minerals be destroyed?

1. Melting

2. Dissolution

3. Chemical Reactions

4. Microbial Metabolism

What is melting?

Heating mineral to the thermal vibration at which atoms/ions in the lattice break the chemical bonds holding them to the lattice.

What is dissolution?

Immerse a mineral in a solvent that separates the ions/atoms from a crystal face and is surrounded by solvent molecules.

What is a chemical reactions?

Destroys a mineral by coming into contact w/ reactive materials.

What is a microbial metabolism?

Destroys minerals; can “eat” certain minerals, then uses the energy stored in the chemical bonds that hold the atoms of the mineral together as their sources of energy for metabolism.

What are the ways you can tell minerals from each other?

1. Color

2. Streak

3. Luster

4. Hardness

5. Specific Gravity (Density)

6. Crystal Habit

7. Special Properties

8. Fracture/Cleavage

What is color?

How minerals interact w/light; Reveals what was absorbed.

What is streak?

The color of a powder produced by pulverizing the mineral.

What is hardness?

Ability to resist scratching.

What is specific gravity? (Density)

Ratio between weight of volume and weight of an equal volume of water at 4 Celsius

What is crystal habit?

Shape of a single crystal with well formed crystal faces; aggregate of many well formed crystals that grow together as a group.

What are special properties?

Distinguished materials.

What is cleavage?

A mineral breaks in orientation to a crystal structure. (Cleavage Plane)

What is fracture?

Break irregularly or conchoidal smooth fractures.

Silicon-Oxygen Tetrahedron

four oxygen atoms surround a single silicon atom, thereby defining the corners of a tetrahedron.

What is an independent tetrahedra?

Do not share any oxygen atoms; positive and forms a solid network,

What is a single chain?

Tetrahedra link to form a chain by sharing two oxygen atoms.

What is a double chain?

tetrahedra link by sharing two or three oxygen atoms.

What is a sheet silicate?

All the tetrahedra in this group share three oxygen atoms and therefore link to form two-dimensional sheets.

What is a framework silicate?

each tetrahedron shares all four oxygen atoms with its neighbors, so the tetrahedra are configured in a three-dimensional structure.

What is a gemstone?

Special value due to rarity

What is a gem?

A finished stone ready to be set in jewelry.

Label these parts.

:o)

What are facets?

Ground and polished surface of a gem.