1. Minerals
Chapter 5

2. Minerals
naturally occurring; non living; solid that has a definite composition and structure
4000 different minerals
naturally occurring- not made by man
inorganic- not alive, never was alive, didn’t come from living materials
definite structure- atoms arranged in repeating patterns
definite composition- specific chemical formula
barite (BaSO4)
talc [Mg3Si4O10(OH)2]

4. 2 Main Composition Groups
silicates
(largest group) -Si & -O
non-silicates
carbonates -CO3
oxides -O
sulfides -S
halides -Cl or -F
sulfates -SO4
native elements not combined with any other atom

6. Crystal Systems Atoms arranged in repeating patterns
Not all samples show flat sides and sharp edges, it depends on where and conditions of the sample when it formed
Constrictive environment creates small crystals, or masses of interlocking crystals
Not restrictive environment allows crystals to grow large

7. How Minerals Form Cooling of hot magma (hot melted rock)
Liquids containing the mineral evaporates, leaving the mineral

8. 6 Major Crystal Systems Cubic- (halite) Orthorhombic- (sulfur)
Tetragonal
Monoclinic- (gypsum)
Hexagonal- (quartz)
Triclinic
why 6?
Lengths of the axis and the angles at which the axis intersect determines the crystal system

10. Physical Properties
Unique properties or descriptions that help to identify minerals
Hardness
Luster
Color
Streak
Cleavage vs. Fracture
Specific Gravity
Special properties

11. Hardness How easily a mineral can be scratched
Mohs Hardness Scale Tools
talc
gypsum fingernail*
calcite copper penny*
fluorite iron nail
apatite glass plate*
feldspar steel file
quartz streak plate*
topaz
corundum * tools we will use in lab.
diamond to determine a mineral’s hardness
A higher number mineral will scratch a lower number mineral

12. Luster How light is reflected from a mineral
metallic—shines like a metal
nonmetallic—does not shine like a metal
can be dull, pearly, glassy, silky, brilliant

13. Color Look at mineral to recognize the color
Usually a bad way to identify minerals, because most minerals can be different colors
sulfur, olivine, orthoclase, malechite, copper

14. Streak the color of the mineral in powder form
Use streak plate for minerals with hardness less than 7!

15. Cleavage Tendency for a mineral to break along smooth flat surfaces
Why?
Orderly arrangement of atoms causes a weakness where bonds aren’t as strong. Relates chemical makeup and chemical structure
Cleavage is expressed in number of directions of cleavage & the angles at which they intersect

16. Directions of Cleavage
1 direction—sheets of paper
2 directions—a box with open top and bottom
3 directions—a brick
Can have more than three, but it is difficult to see except in a fluorite octahedral

17. Angles of Cleavage
Angles between the directions of cleavage are either 90o or NOT 90o
Also described as perfect (easy to see) or poor (hard to see)

18. Fracture curved, broken of jagged edges without flat surfaces
special type of fracture—conchoidal fracture looks like a shell with curved pattern seen in quartz

19. Specific Gravity
Mass per unit of volume compared to H2O (density of mineral compared to the density of water)
It is heavy for it’s size??

20. Special Properties Optical properties- transparent or translucent
double refraction of calcite 
Reaction to acid- members of the carbonate group fizz when put into acid…CO2 gas bubbles
ex. calcite, malachite 
Magnetism- some minerals are magnetic, others are attracted to a magnet
ex. magnetite
Taste
ex. halite is “salty”

21. Special Properties Iridescence- rainbow colors like soap bubbles
ex. Labradorite
Chatoyancy- cat’s eye effect
Asterism- six sided star appears in the mineral
Phosphorescence or fluorescence- how minerals behave in ultraviolet light. Some change colors, some glow in the dark