1. Objectives Vocabulary Define a mineral. Describe how minerals form.
What is a mineral?
Objectives
Define a mineral.
Describe how minerals form.
Identify the most common elements in Earth’s crust.
Vocabulary
mineral
crystal
magma
silicate

2. What is a mineral? Earth’s crust is composed of about 3000 minerals.
Minerals play important roles in forming rocks and in shaping Earth’s surface, and a select few have played a role in shaping civilization.

3. Mineral Characteristics
What is a mineral?
Mineral Characteristics
A mineral is a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure.
Naturally Occurring and Inorganic
That minerals are naturally occurring means that they are formed by natural processes.
All minerals are inorganic, meaning that they aren’t alive and never were alive during any part of their existence.

4. Mineral Characteristics
What is a mineral?
Mineral Characteristics
Solids with Specific Compositions
All minerals are solids with definite shapes and volumes.
Each type of mineral has a chemical composition unique to that mineral.
Although a few minerals, such as copper, silver, and sulfur, are composed of single elements, the vast majority are made from compounds.
In some minerals, chemical composition may vary within a well-defined range.

5. Mineral Characteristics
What is a mineral?
Mineral Characteristics
Definite Crystalline Structure
The atoms in minerals are arranged in regular geometric patterns that are repeated again and again.
A crystal is a solid in which the atoms are arranged in repeating patterns.

6. Mineral Characteristics
What is a mineral?
Mineral Characteristics
Definite Crystalline Structure
At times and fairly rare, a mineral will form in an open space and grow into one large crystal, possibly taking the shape of one of the six major crystal systems.
Tetragonal
Orthorhombic
Triclinic
Hexagonal
Monoclinic
Cubic

7. Minerals from Magma Minerals can form from the cooling of magma.
What is a mineral?
Minerals from Magma
Minerals can form from the cooling of magma.
Magma is molten material found beneath Earth’s surface.
The type and amount of elements present in the magma help determine which minerals will form as it cools.
Small crystals form from rapidly cooling magma and large crystals form from slowly cooling magma.

8. Minerals from Solution
What is a mineral?
Minerals from Solution
A given volume of water in a solution can dissolve only so much of a solid before the water becomes saturated.
If a solution becomes supersaturated, or overfilled, with another substance, mineral crystals may begin to precipitate, or drop out of solution.
When liquid evaporates from a supersaturated solution, the elements remain behind and may begin to arrange into crystals.

9. Mineral Groups About 30 minerals are common in Earth’s crust.
What is a mineral?
Mineral Groups
About 30 minerals are common in Earth’s crust.
The most common minerals are often referred to as rock-forming minerals because they make up most of the rocks found in Earth’s crust.
The vast majority of minerals are made up of the eight most common elements.

10. What is a mineral?
Mineral Groups

11. Mineral Groups Silicates
What is a mineral?
Mineral Groups
Silicates
Silicates are minerals that contain silicon and oxygen, and usually one or more other elements.
Silicates make up approximately 96 percent of the minerals found in Earth’s crust.
The most common minerals, feldspar and quartz, are silicates.

12. Mineral Groups Silicates
What is a mineral?
Mineral Groups
Silicates
One silicon atom attaches to four oxygen atoms to form a silica tetrahedron, a three-dimensional shape structured like a pyramid.
The basic silica tetrahedron has the ability to share oxygen atoms with other tetrahedron molecules.
This allows the molecules to combine chemically and structurally in a vast number of ways.

13. Mineral Groups Silicates
What is a mineral?
Mineral Groups
Silicates
Some possible arrangements formed by silica tetrahedrons include single chains, double chains, and sheets.

14. What is a mineral?
Mineral Groups
Silicates

15. Mineral Groups Carbonates
What is a mineral?
Mineral Groups
Carbonates
Carbonates are minerals composed of one or more metallic elements with the carbonate compound CO3.
Carbonates are the primary minerals found in rocks such as limestone, coquina, and marble.

16. Mineral Groups Oxides Oxides are compounds of oxygen and a metal.
What is a mineral?
Mineral Groups
Oxides
Oxides are compounds of oxygen and a metal.
Hematite (Fe2O3) and magnetite (Fe3O4) are common iron oxides and good sources of iron.

17. What is a mineral?
Mineral Groups
Oxides
Other major mineral groups are sulfides, sulfates, halides, and native elements.
Sulfides such as pyrite (FeS2) are compounds of sulfur and one or more elements.
Sulfates such as anhydrite (CaSO4) are composed of elements with the sulfate compound SO4.
Halides such as halite (NaCl) are made up of chloride or fluoride along with calcium, sodium, or potassium.
A native element such as silver (Ag) or copper (Cu) is made up of one element only.

18. What is a mineral?
Mineral Groups

19. Objectives Vocabulary
Identifying Minerals
Objectives
Classify minerals according to their physical and chemical properties.
Identify different types of minerals.
Discuss how minerals are used.
Vocabulary
luster
streak
hardness
cleavage
fracture
specific gravity
ore
gem

20. Mineral Identification
Identifying Minerals
Mineral Identification
Geologists rely on several relatively simple tests to identify minerals.
These tests are based upon a mineral’s physical and chemical properties.
It is usually best to use a combination of tests rather than just one to identify minerals.

21. Mineral Identification
Identifying Minerals
Mineral Identification
Color
One of the most noticeable characteristics of a mineral is its color.
Color is sometimes caused by the presence of trace elements or compounds within a mineral.
In general, color is one of the least reliable clues to a mineral’s identity.

22. Mineral Identification
Identifying Minerals
Mineral Identification
Luster
Luster is the way that a mineral reflects light from its surface.
Luster is described as being either metallic or nonmetallic.
Metallic luster describes shiny surfaces that reflect light like the chrome trim on cars.
Nonmetallic luster might be described as dull, pearly, waxy, or silky.
Differences in luster are caused by differences in the chemical compositions of minerals.

23. Mineral Identification
Identifying Minerals
Mineral Identification
Texture
Texture describes how a mineral feels to the touch.
The texture of a mineral might be described as smooth, rough, ragged, greasy, soapy, or glassy.

24. Mineral Identification
Identifying Minerals
Mineral Identification
Streak
Streak is the color of a mineral when it is broken up and powdered.
Sometimes, a mineral’s streak does not match the mineral’s external color.
A mineral’s streak rarely changes, even if it is weathered or its external color varies slightly.

25. Mineral Identification
Identifying Minerals
Mineral Identification
Hardness
Hardness is one of the most useful and reliable tests for identifying minerals.
Hardness is a measure of how easily a mineral can be scratched.
German geologist Friedrich Mohs developed a scale in which an unknown mineral’s hardness can be compared to the known hardnesses of ten minerals.
Any mineral with a greater hardness than another mineral will scratch that softer mineral.

26. Mineral Identification
Identifying Minerals
Mineral Identification
Hardness

27. Mineral Identification
Identifying Minerals
Mineral Identification
Cleavage and Fracture
Minerals break along planes where atomic bonding is weak.
Cleavage is the ability of a mineral to split relatively easily and evenly along one or more flat planes.
To identify a mineral by cleavage, geologists count the number of cleaved planes and study the angle or angles between them.
Fracture is the ability of minerals to break with arclike, rough, or jagged edges.

28. Mineral Identification
Identifying Minerals
Mineral Identification
Density and Specific Gravity
Differences in weight are the result of differences in density, which is defined as mass per unit of volume.
Density is expressed as a ratio of the mass of a substance divided by its volume, or D = M/V.
Density reflects the atomic weight and structure of a mineral.
The most common measure of density used by geologists is specific gravity.
Specific gravity is the ratio of the weight of a substance to the weight of an equal volume of water at 4°C.

29. Identifying Minerals
Special Properties
Special properties of minerals also can be used for identification purposes.
A type of calcite called Iceland spar causes light to be bent in two directions, a process known as double refraction, when it passes through the mineral.
Calcite (CaCO3) fizzes when it comes into contact with hydrochloric acid (HCl).
Magnetite, an iron ore, is naturally magnetic.
The mineral sphalerite produces a distinctive rotten-egg odor when it is rubbed vigorously across a streak plate.

30. Mineral Uses Minerals are virtually everywhere.
Identifying Minerals
Mineral Uses
Minerals are virtually everywhere.
They are used to make computers, cars, televisions, desks, roads, buildings, jewelry, beds, paints, sports equipment, and medicines, just to name a few uses.

31. Identifying Minerals
Mineral Uses
Ores
An ore is a mineral that contains a useful substance that can be mined at a profit.
Examples of ores include Hematite, which contains the element iron and bauxite, which contains the element aluminum.

32. Identifying Minerals
Mineral Uses
Mines
Ores are removed by underground mining or from large, open-pit mines.
When a mine is excavated, unwanted rock and dirt, known as waste material, are dug up along with ore.
If the cost of separating the waste material becomes higher than the value of the ore itself, then the mineral will no longer be classified as an ore because it would no longer be economical to mine it.
The classification of a mineral as an ore may also change if the supply of or demand for that mineral changes.

33. Identifying Minerals
Gems
Gems are valuable minerals that are prized for their rarity and beauty.
Gems such as rubies, emeralds, and diamonds are cut, polished, and used for jewelry.
In some cases, the presence of trace elements can make one variety of a mineral more colorful and thus more prized than other varieties of the same mineral.