1. Minerals

2. Minerals: Building blocks of rocks
To be considered a mineral, a substance must:
be a naturally occurring solid
be formed by inorganic processes
have a crystalline structure (orderly molecular arrangement)
have a specific chemical composition

3. An element is a substance that cannot be broken down into simpler substances by chemical means
Minerals are made up of one or more elements

4. Most abundant elements of the continental crust
Common rock-forming minerals are mostly chemical compounds made up of these elements
How do these elements combine to make minerals?

5. Atoms, molecules and ions
Atoms are the smallest individual particle that retains the distinctive chemical properties of an element.
Molecules are the smallest individual particle that retains the distinctive chemical properties of a chemical compound. Molecules consists of 2 or more atoms.
Ions are atoms or molecules that have a net electrical charge. They attract oppositely-charged ions to form chemical compounds.

6. Crystalline Nature of Minerals
Crystal: any substance whose atoms are arranged in a regularly repeating pattern
Crystal growth is often interrupted due to:
lack of space
rapid cooling rate

7. Luster: Appearance of a mineral in reflected light
Metallic (pyrite)
Nonmetallic: glassy/pearly (potassium feldspar)

8. Luster: Appearance of a mineral in reflected light
Nonmetallic- waxy (ex: chert)
Nonmetallic –greasy (quartz)

9. Color
Often highly variable for a given mineral due to slight impurities in crystal structure
For example, quartz (SiO2) exhibits a variety of colors

10. Other Physical properties of minerals
Streak
Color of a mineral in its powdered form
Helpful in distinguishing different forms of the same mineral
Hardness
Resistance of a mineral to abrasion or scratching
All minerals are compared to a standard scale, the Mohs Scale of Hardness.

11. Streak – the color of a powdered mineral
Figure 2.10

12. Hardness Resistance of a mineral to abrasion or scratching
All minerals are compared to a standard scale called the Mohs scale of hardness

13. Cleavage Tendency to break along planes of weak bonding
Produces flat, shiny surfaces
Described by resulting geometric shapes, and
Number of planes
Angles between adjacent planes
Cleavage is one of the physical diagnostic properties of minerals. To cleave means to break and cleavage is the tendency of a mineral to break along planes of weak chemical bonding, which we call cleavage planes.If a mineral breaks along a cleavage plane, it produces flat, shiny surfaces. If it breaks along a non-cleavage plane, the result will be jagged and irregular.

14. Three examples of perfect cleavage – fluorite, halite, and calcite
Imagine every mineral as a 3 dimensional shape. Each plane is represented by 2 sides (top and bottom, front and back, left and right.
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15. Common cleavage directions
Cleavage is described by the number of cleavage planes the angle between adjacent planes and the shape of the mineral if it breaks along cleavage planes

16. Classification of Minerals
Rock-forming minerals
Common minerals that make up most of the rocks of Earth’s crust
Only a few dozen members
Composed mainly of the 8 elements that make up over 98% of the continental crust

17. 8 most common elements

18. Classification of Minerals
In most cases, minerals are grouped according to the major “building block” in the chemical structure.
Silicates (SiO44-)
Oxides (O22-)
Sulfides (S2-)
Sulfates (SO42- )
Carbonates (CO32-)
Halides (Cl1- , F1- Br1- )
Native Elements (single element)

19. Rock-forming Minerals – The Silicate Group
Most common mineral group due to large amounts of silicon and oxygen in Earth’s crust
Basic building block is the silicate ion: Four oxygen ions surrounding a much smaller silicon ion.
Polymerization: process by which silicate ions bond to form more complex ions, such as rings, chains, sheets or 3 dimensional frameworks.

20. Common Silicate minerals
Olivine Group
High temperature Fe-Mg silicate
Individual silicate linked together by iron and magnesium ions
Forms small, rounded crystals with no cleavage

21. Common Silicate minerals
Pyroxene Group
Single chain structures involving iron and magnesium
Two distinctive cleavages at nearly 90 degrees

22. Common Silicate Minerals
Amphibole Group
Double chain structures involving a variety of ions linking the silicate ion
Two perfect cleavages at non right angles Hornblende is the most common mineral in the amphibole group

23. Common Silicate Minerals
Mica Group
Sheet structures that result in one direction of perfect cleavage
Biotite is the common dark colored mica.

24. Common Silicate Minerals
Mica Group
Sheet structures that result in one direction of perfect cleavage
Muscovite is the common light colored mica.

25. Classification of Minerals
Common Silicate minerals
Feldspar Group
Most common mineral group
3-dimensional framework that exhibits two directions of cleavage at 90 degrees
(potassium feldspar) (e.g. Orthoclase or Microcline)
Plagioclase (sodium and calcium feldspar) are the two most common members

26. Feldspar Minerals

27. Potassium feldspar - Orthoclase
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28. Calcium-rich plagioclase feldspar

29. Quartz
Consists entirely of silicon and oxygen (SiO2). This is a material called silica.
Strong bonds in all directions – cleavage absent.
Naturally clear, but impurities cause colors.

30. Chert – Cryptocrystalline Quartz

31. Nonsilicate mineral groups
Fluorite (left, calcium fluoride) and halite (right, sodium chloride) are members of the Halide mineral group. The minerals in this group have, as part of the chemical structure, an ion from the halogen elements: Fl1- , Cl1- , I1- , or Br1- .
Gypsum (calcium sulfate) is a member of the sulfate group. The building block for minerals in this group is the sulfate ion, SO42- .

32. The Carbonate Group
Carbonates are minerals found in exoskeletons of marine organisms.
Calcite (calcium carbonate – CaCO3) is the most important carbonate mineral.
It has a nearly perfect rhomboid cleavage
It will dissolve if exposed to acid (as shown in the video).
“Strong bones, strong teeth”

33. Nonsilicate Rock-forming mineral groups
Sulfates – minerals containing the sulfate ion
Gypsum (Calcium sulfate: CaSO4 – 2H2O. A product of rapid evaporation of ancient seas.