1. Minerals

2. What is a mineral?
A mineral is a naturally occurring, inorganic solid with an orderly crystalline structure and a definite chemical composition

3. 5 Characteristics of Minerals
1. Naturally occurring- forms by natural geologic processes, synthetic gems are not considered minerals
2. Solid Substance- within temperature ranges that occur at Earth’s surface
3. Orderly crystalline Structure- atoms are arranged in an orderly and repetitive manner
4. Definite Chemical Composition- minerals are chemical compounds made up of a two or more elements (exception- native elements)
5. Generally Considered Inorganic- table salt is inorganic, sugar is organic and is not a crystal. Sugar comes from a plant
Calcium carbonate- secreted by marine animals, inorganic or organic?

4. How do minerals form? Four major processes by which minerals form
1. Crystallization from magma
2. Precipitation
3. Pressure and Temperature
4. Hydrothermal Solutions

5. Crystallization of Magma
Magma is molten rock that occurs deep within the Earth
As magma cools, elements combine to form minerals
First minerals formed are rich in iron, calcium, magnesium
Next are minerals rich in sodium, potassium, and aluminum

6. Precipitation
Minerals form when water evaporates in lakes, rivers, ponds, and oceans
Minerals are left behind or precipitated from the water
Halite and calcite form this way

7. Pressure and Temperature
Some minerals from when others are subject to changes in pressure and temperature
Atoms are rearranged to form more compact minerals
Talc and muscovite are formed this way

8. Hydrothermal Solutions
Hydro (water) thermal (heat)
Very hot mixtures of water and dissolved substances
Can have temperature between 100oC and 300oC
Chemical reactions occur at these temperatures causing minerals to form, or as solution cools minerals form

9. Mineral Groups
There are over 3800 named minerals on Earth and more are identified each year
Common Minerals are classified into groups based on their composition
Seven mineral groups-
Silicates, carbonates, oxides, sulfates, sulfides, halides, native elements

10. Silicates
These are the most common- remember from chemistry unit, the most abundant elements in Earth’s crust are oxygen and silicon
Silicon-oxygen tetrahedron- structure which consists of one silicon to four oxygen molecules (most silicates occur in this form)
Most silicate minerals form from crystallization of magma near or far below earth’s surface
Examples include- quartz, augite, micas

11. Carbonates Second most abundant mineral group
Contain carbon, oxygen, and one or more other metallic elements
Examples include calcite, dolomite, limestone, marble

12. Oxides
Oxides contain oxygen and one or more other elements, which are usually metals
Some form under Earth’s surface from crystallization of magma (rutile), others from when minerals are subject to changes in temperature and pressure (corundum), others form when a mineral is exposed to liquid water (hematite, iron oxide)

13. Sulfates and Sulfides Both contain sulfur
Sulfates- (anhydrite, and gypsum) form when mineral rich waters evaporate
Sulfides- (galena, sphalerite, pyrite) form from hydrothermal solutions

14. Halides
This group contains a halogen ion plus one or more other elements
Halogens occur in group 17 (7a) of the periodic table
Examples include- halite and fluorite

15. Native Elements This group occurs in pure elemental form
Examples include- gold, silver, copper, sulfur, carbon (graphite and diamonds)

16. Properties of Minerals and Mineral Identification
Properties of minerals are determined by composition and structure
Color
Streak
Luster
Crystal Form
Hardness
Cleavage
Fracture
Density
Unique properties include- magnetism, double refraction, chemical reactions with HCl

17. Color and Luster
Color can be unique to some minerals, but for most it is not the most useful for identification
Color within minerals can vary depending on other elements present within the mineral
Luster- how light is reflected from the surface of a mineral
Metallic (metal like), vitreous/glassy (quartz), pearly, silky, earthy

18. Streak and Crystal Form
Color of a mineral in its powdered form
We can use a streak plate (a sheet of unglazed porcelain) to determine this property
Crystal form- visible expression of internal arrangement of atoms
When a mineral forms without any space restrictions it will develop into a perfect crystal with well developed faces
6 Crystal Forms

19. Type 1: Isometric (Cubic)
6 sides
All sides are square
Examples
*pyrite
*halite
*diamond
*galena

20. Type 2: Tetragonal 6 sides 4 rectangles, 2 squares (right angles)
Example
*zircon

21. Type 3: Hexagonal 8 sides 2 hexagons, 6 rectangles (right angles)
Examples
*ice
*quartz
*emeralds

22. Type 4: Orthorhombic 6 sides
6 rectangles (3 pairs of rectangles with different sizes at right angles)
Examples
*topaz
*barite

23. Type 5: Monoclinic 6 sides
4 rectangles, 2 parallelograms (several angles)
Examples
*gypsum
*muscovite

24. Type 6: Triclinic 6 sides Parallelograms (no right angles) Example
*turquoise

25. Mineral with a Cubic or Isometric Crystal Shape
Pyrite has a Cubic Crystal Structure

26. Mineral with a Tetragonal Crystal Shape
Rutile has a Tetragonal Crystal Structure

27. Mineral with a Hexagonal Crystal Shape
Ruby has a Hexagonal Crystal Structure

28. Minerals with Orthorhombic Crystal Shapes
The is a very big crystal system containing gemstones such as topaz, peridot, tanzanite, and many others

29. Mineral with a Monoclinic Crystal Shape
Gypsum is a mineral with a Monoclinic Crystal Structure

30. Mineral with a Triclinic Crystal Shape
Calcite- Triclinic crystal look like a rectangular box that someone pushed from one side to make it lean

31. Hardness One of the more useful properties for identification
Done by rubbing two minerals together, one will scratch the other unless they have the same hardness
Mohs Hardness Scale- 1-10
Talc is the softest, what is hardest?

32. Moh’s Hardness Scale

33. Cleavage and Fracture
Cleavage is the tendency of a mineral to cleave or break along flat, even surfaces
Fracture is what happens to all other minerals that do not display cleavage
Fracture can be described as the uneven breakage of a mineral
Internal atomic structure determines whether a mineral will display cleavage or fracture

34. Fracture or Cleavage?
Selena

35. Density Ratio of an objects mass to its volume D= M/V
For minerals we would use g/cm3, since we are looking at solids
Density of pure minerals are of constant value. Therefore we can use density to identify pure minerals or to tell if a mineral is not in pure form.

36. Other Properties
Magnetism- some types of magnetite are magnetic and can be used to pick of metal objects
Double Refraction- When calcite is placed over printed words the letters appear doubled
Chemical Reactions with HCl- Carbonate minerals will fizz when they come into contact with hydrochloric acid

37. Double Refraction of Calcite

38. Magnetism