Chapter 3 Minerals. Minerals: naturally occurring, inorganic solids, with definite structure and...
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Transcript of Chapter 3 Minerals. Minerals: naturally occurring, inorganic solids, with definite structure and...
• Minerals: naturally occurring, inorganic solids, with definite structure and composition; made of one or more elements
– Characteristics of Minerals:• Formed by natural processes• Inorganic (not formed from life processes)• Solid• Definite chemical composition, can have minor
variations (example: salt is NaCl)• Atoms arranged in a pattern
Structure of Minerals: minerals are in the form of crystals (a solid in which the atoms are arranged in repeating patterns)
A.Crystal Systems: Examples of Perfect Crystal Systems
Cubic Tetragonal Hexagonal
Examples: Cubic-Halite (salt); Platinum Tetragonal-Zircon; Wulfenite
Hexagonal-Quartz; Corundum
The first group is the ISOMETRIC. This literally means “equal measure” and refers to the equal size of the crystal axes.
ISOMETRIC - Fluorite Crystals
CRYSTAL SYSTEMS are divided into 6 main groups.- We will look at 3 groups
ISOMETRIC Basic Cube
a3
a2
a1
These hexagonal CALCITE crystals nicely show the six sided prisms
HEXAGONAL CRYSTALS
HEXAGONAL Crystal AxesThree horizontal axes meeting at angles of 120o and one perpendicular axis.
c
aa3 a2
a1
TETRAGONAL Crystal Axes
a1a2
cc
a2a1
This is an Alternative Crystal Axes
TETRAGONAL Two equal, horizontal, mutually perpendicular axes (a1, a2) Vertical axis (c) is perpendicular to the horizontal axes and is of a different length.
TETRAGONAL CRYSTALS
How Minerals Form:
Form from the cooling of hot melted rock (magma); If it cools fast, crystals tend to be small; cools slow, larger crystals tend to form
Form from solutions-as liquid evaporates, minerals solidify and form crystals
Major Mineral Groups
Silicates-Made of Silicon, Oxygen, & possibly other element(s); largest group of minerals
Example: Quartz (SiO2)
Carbonates-Made of Carbon, Oxygen, & possibly other element(s)
Examples: Calcite (CaCO3); Magnetite (MgCO3)
Most Abundant Elements in Earth’s Crust:
1. Oxygen 46.6%2. Silicon 27.7%3. Aluminum 8.1%4. Iron 5%5. Calcium 3.6%6. Sodium 2.8%7. Potassium2.6%8. Magnesium 2.1% ***All other elements make up 1.5% of the Earth’s
crust.
Physical Properties of Minerals:
Hardness-a measure of how easily a mineral can be scratched
***1 is the softest, 10 is the hardest***
Moh’s Scale of Hardness
Sample Element
HardnessCommon
Objects
Talc 1 Fingernail (2.5)Copper penny
(3.5)Iron Nail (4.5)
Glass (5.5)Steel File (6.5)Streak Plate (7)
Gypsum 2
Calcite 3
Fluorite 4
Apatite 5
Feldspar 6
Quartz 7
Topaz 8
Corundum 9
Diamond 10
Luster Describes how light is reflected from a
mineral’s surface– Metallic– Nonmetallic– dull; pearly; silky; glassy; brilliant; transparent– Waxy– Resinous (looks like freshly broken shellac)
Color
The color seen when looking at the surface of the mineral; Least reliable property because many minerals can be many colors
Example: Sulfur is pale yellow
Streak The color of the mineral when it’s broken up in
powdered form; Use a porcelain tile to test; Useful for softer minerals; Minerals with a hardness greater than 7 do not leave a streak
Example: Gold has a gray streak
The Way a Mineral Breaks
1. Cleavage-When a mineral breaks along smooth, flat surfaces; Example: Mica
2. Fracture-When minerals break with rough or jagged edges; Example: Quartz
Special Properties Unusual or unique qualities; Examples:
Magnetite is magnetic, Calcite has optical qualities, Jade has a bell-like ring when tapped, Halite has a salty taste, and Sulfur smells like rotten eggs
Uses of Minerals
Gems-Highly prized minerals because they are rare and considered beautiful; the difference in a gem and the common form of a mineral can be slight
Ores-contain useful substances that can be mined for a profit
Examples: Bauxite contains Aluminum
Hematite contains Iron
Sphalerite contains Zinc
Chalcopyrite contains copper
• Strip Mining-Removing ore by digging at Earth’s surface; usually results in a huge pit
• Land Reclamation- mining companies are required to return soil and rock to open pit and cover it with topsoil then plant trees and grass
Asbestos-a mineral with threadlike, flexible fibers used as insulation and as fire protection; has been shown to cause lung diseases including lung cancer
EPA (Environmental Protection Agency)-requires school officials to inspect buildings every six months; flaking asbestos must be removed or sealed over
Minerals can contain other useful elements.
1.Elements must be refined, or purified, from ores
2. Some elements dissolve in fluids, travel through weaknesses in rocks, and in those weaknesses form mineral deposits called vein mineral deposits
3. Titanium is useful element derived from the minerals limonite and rutile