1. Chapter 2 Section 2
Minerals

2. What is a mineral? What are the components of a mineral?
Naturally occurring
Solid substance
Inorganic
Orderly crystalline structure
Definite chemical composition
Ex: Quartz  SiO2 (silicon & oxygen)
ALL rocks are COMPOSED of minerals

3. 1. Naturally Occurring
Minerals are formed by natural, geologic processes
Must naturally occur in nature, cannot be man-made
i.e. synthetic gems are not considered minerals.
Chillagoe caves,Austrailia

4. 2 & 3. Inorganic Solid Substance
Minerals are a solid….
not a liquid…not a gas.
within temperature
ranges that are normal for
Earth.
Inorganic crystalline solids found in nature
Table salt is a mineral  inorganic
Sugar is not mineral  organic
Exception: many marine animals secrete inorganic compounds
calcium carbonate minerals (coral reefs and in shells)

5. 4. Crystalline Structure
Atoms are arranged in an orderly, repetitive structure (crystal lattice)
Ex: gemstone opal isn’t a mineral has the same elements as quartz (mineral) but NO orderly internal structure

6. 5. Chemical Composition Au Pyrite “Fools Gold” FeS2
A mineral has a chemical composition defined by a chemical formula
Compounds made of 2+ elements
Exceptions: gold & silver  1 element (native form)

7. How Minerals Form 4 major processes by which minerals form:
Crystallization from magma
Precipitation
Changes in pressure and temperature
Formation from hydrothermal solutions

8. Crystallization from Magma
Magma = molten rock
Magma cools elements combine to form minerals
Ex: quartz & feldspar
First to crystallize ones rich in iron, calcium, and magnesium
Each mineral begins to crystallize at a different temperature

9. Precipitation
All water in Earth’s lakes, rivers, oceans etc. contain dissolved substances
Water evaporates  dissolved substances react to form minerals
Change in water temperature  dissolved material precipitates out
Supersaturated
Ex: limestone caves,
Great Salt Lake, Utah
Mono Lake, CA limestone towers (calcite) formed underwater from calcium rich springs  exposed as sea level drops

10. Pressure & Temperature
Existing minerals subjected to changes in pressure and temperature
Increase pressure
Minerals recrystallize while still solid
Atoms rearranged  forms compacted minerals
Change in temperature
Minerals may become unstable
Form new minerals  new temperature

11. Hydrothermal Solutions
Very hot mixture of water & dissolved substances
Have temps. between 100°C and 300°C
Solutions come in contact w/ existing minerals chemical reactions occur  new minerals
Solutions cool  elements combine
Supersaturated
Ex: Bornite and chalcopyrite (sulfur minerals) formed from thermal solutions

12. Mineral Groups
Common minerals, together with the thousands of others that form on Earth, can be classified into groups based on their composition.
Silicates
Carbonates
Oxides
Sulfates and sulfides
Halides
Native elements
Fluorite - a halide
Okenite - a silicate
Galena - a sulfide

13. Silicate Structure Most common group
Silicon and oxygen combine to form a silicon-oxygen tetrahedron
Tetrahedron consists of 1 silicon atom & 4 oxygen atoms  silicate
Silicon-oxygen tetrahedra can form chains, sheets, & 3-D networks
Super strong bonds
Ex: olivine-millions of single tetrahedra
(Fe,Mg)2SiO4) iron-magnesium silicate

14. Silicate Formation
Most silicate minerals crystallize from magma as it cools
Can occur at or near surface of Earth (temp. and pressure low)
Weathering & mountain building  form silicates
Can occur at great depths (temp. and pressure high)
Location during formation & chemical composition of magma determines which silicate minerals will form
Olivine: 1200°C Quartz: 700°C

15. Carbonates 2nd most common mineral group Contain the elements:
oxygen
one or more other metallic elements
Calcite (CaCO3): most common carbonate mineral
Limestone & marble  rocks that are composed of carbonate minerals

16. Oxides Contains: Ex: Rutile (TiO2) Ex: Corundum (Al2o3) Oxygen
One or more other elements (usually metals)
Ex: Rutile (TiO2)
Form as magma cools beneath Earth’s surface
Titanium oxide
Ex: Corundum (Al2o3)
Existing minerals  heat & pressure
Aluminum oxide

17. Sulfates and Sulfides Contain the element sulfur Sulfates = Sulfides =
Ex: Anhydrite (CaSO4)
Ex: Gypsum (CaSO4  2H2O)
Forms when mineral-rich water evaporates
Sulfides =
Ex: Galena (PbS)
Ex: Pyrite (FeS2)
Forms from thermal solutions

18. Halides Contains: Halogens from Group 7A in periodic table
Halogen ion
One or more other elements
Halogens from Group 7A in periodic table
Includes fluorine and chlorine
Halite (NaCl) i.e. table salt
Fluorite (CaF2) used in making steel
Forms when salt water evaporates

19. Native Elements Minerals in relatively pure form
Ex: Gold (Au), Silver (Ag), Copper (Cu), Sulfur (S), Carbon (C)
Native forms of carbon are diamond and graphite
Some form from hydrothermal solutions