1. Learning Target = Matter & Minerals

2. Mineral Characteristics
Definition = naturally occurring, inorganic solid with an orderly crystalline structure and a definite chemical composition
To be considered a mineral, must have the following characteristics:
Naturally occurring
Solid substance
Orderly crystalline structure
Definite chemical composition
Generally considered inorganic

3. Mineral Characteristics
Naturally occurring – formed by geologic processes
Solid substance – solids within temp ranges that are normal for Earth’s surface
Crystalline structure – atoms or ions arranged in orderly & repetitive manner
Definite chemical composition – most minerals are chemical compounds
Generally considered inorganic – minerals generally do not come from a living source

4. How Minerals Form 4 major processes by which minerals form:
Crystallization from Magma
Precipitation
Pressure & Temperature
Hydrothermal Solutions

5. How Minerals Form Crystallization from Magma
As magma (molten rock) cools, elements combine and crystallize
1st – compounds rich in Fe, Ca, Mg
2nd – Na, K, Al
Muscovite
Feldspar
Horneblende
Quartz

6. How Minerals Form Precipitation Water contains dissolved substances
Minerals form due to:
Evaporation
Temperature change
Minerals are left behind

7. How Minerals Form Pressure & Temperature
Increase in pressure causes a mineral to recrystallize
Form more compact minerals
Temperature change can cause instability and new minerals form that are stable at new temperature
Ex: Talc & Muscovite

8. How Minerals Form Hydrothermal Solutions
Hot mixture of water & dissolved substances
Temps = 100°C & 300°C
Chemical reactions form new minerals
Solutions cool & minerals form as well
Ex: Quartz, pyrite, sulfur minerals

9. Mineral Groups Over 3,800 identified minerals
Groups are based on composition
Silicates
Carbonates
Oxides
Sulfates & sulfides
Halides
Native elements

10. Silicates Silicon & oxygen = most abundant elements in Earth’s crust
Si and O combine & form the silicon-oxygen tetrahedron (SiO4)
Usually contain other elements
Si-O tetrahedra join in different ways & bonds are strong

11. Olivine
Augite
Hornblende
Quartz
Mica

12. Silicates Crystallization from magma
Cooling occurs at or near Earth’s surface (temp and pressure low)
Also form at great depths (T & P ↑)
Silicate formation dependent on:
Place of formation
Chemical composition of magma

13. Carbonates 2nd most common group
Contain C, O & another metallic element
Calcite (CaCO3) is most common
Ex: Dolomite, limestone (rock), marble (rock)

14. Oxides Contain O + 1 or more elements (usually metals) Form by:
Magma cooling
Changes in T and P
Exposed to water or moisture in air
Ex: Rutile (TiO2), Corndum (Al2O3), Hematite (Fe2O3)

15. Sulfates & Sulfides Contain Sulfur
Form when mineral-rich waters evaporate
Form from thermal solutions
Ex: Gypsum, Galena, Pyrite

16. Halides Contain a halogen ion plus 1 or more elements
Ex: Halite (NaCl) & Fluorite (CaF2)

17. Native Elements Contains one element
Ex: Gold (Au), Silver (Ag), Copper (Cu), Sulfur (S), Carbon (C)
Native forms of carbon are graphite & diamond
Some form from hydrothermal solutions

18. Properties of Minerals
Color
Streak
Luster
Crystal form
Hardness
Cleavage
Fracture
Density
Distinctive properties

19. Properties of Minerals
Color
Can be unique to some minerals
Not useful in identification
Small amounts of different elements can give the same mineral different colors
Ex: Sapphires

20. Properties of Minerals
Streak
Color of a mineral in its powdered form
Rub mineral across a streak plate
Mineral color may vary but streak does not
Difference between minerals with metallic & nonmetallic lusters

21. Properties of Minerals
Luster
How light is reflected from the surface of a mineral
Metallic luster – appearance of metal
Nonmetallic luster – use different adjectives
Glassy or vitreous
Pearly
Silky
Earthy
Brilliant

22. Properties of Minerals
Crystal form
Visible expression of a mineral’s internal arrangement of atoms
When a mineral forms slowly with plenty of space, develop into a crystal with well-formed sides
Most of the time, minerals compete for space so minerals do not show their crystal form

23. Properties of Minerals
Hardness
Measure of the resistance of a mineral to being scratched
Determined by rubbing one mineral against another of known hardness
Mohs scale consists of 10 minerals arranged from 10 (hardest) to 1 (softest)

25. Properties of Minerals
Cleavage
Tendency of a mineral to break along flat, even surfaces

26. Properties of Minerals
Fracture
Uneven breakage of a mineral
Minerals that do not show cleavage when broken are said to fracture

27. Properties of Minerals
Density
Property of all matter that is the ratio of an object’s mass to its volume
Unit = grams per cubic centimeter (g/cm3)
Many common minerals have densities between 2 & 5 g/cm3

28. Properties of Minerals
Distinctive Properties of Minerals
Some minerals can be recognized by other distinctive properties
Feel (Talc = soapy, graphite = greasy)
Easily shaped (Gold, silver, copper)
Magnetic
Double refraction (appearance doubles)
Smell (sulfur minerals = rotten eggs)
Reacts with hydrochloric acid