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Transcript
Unit 5: Earth History and the Rock
Record
Atoms, Minerals, and Rocks
Definitions: p. 42
• Atom
• Element
• Compound
• The smallest part of an element
that can be identified as that
element
• Substance made of two or more
elements
• Substance that cannot be broken
down into simpler substance by
chemical means
Diamond!
What are Minerals?
• Thousands of them!
• They make up the solid geosphere of earth
• Some flashy…some common. Used in everything from
your cell phone, to jewelry, to cooking…
• 5 part Definition:
1.
2.
3.
4.
5.
Solid
Naturally occuring (not made by people)
Inorganic (not made by plants or animals)
Set chemical make-up the same throughout whole mineral
Set arrangement of atoms (how they are bonded together)
What are minerals made of?
• Rocks are made of
minerals
• Minerals are made
of elements or
compounds of
elements
– Ex. Gold vs. quartz
• Elements are made
of atoms
Made of two elements
SiO2=chemical formula
1 Silicon atom for
every 2 oxygen atoms
Example: “Salt”=Halite
•
•
•
•
Solid
Inorganic
Naturally occuring
NaCl=set
chemical
composition
• Set arrangement
of atoms
Elements form Compounds
• 100s of different
elements, most solid at
room temperature
• Combining 2 or more
elements creates
compounds with
different properties than
their elements!
• Compounds have set
proportions (H2O)
Common Minerals
• Less than 20 of the
thousands of
minerals are
common
• Minerals made with
silicon and oxygen
are the most
common (silicate
minerals)
Rare Mineral Resources
• Minerals containing
metals are important
resources
• Minerals that are
hard, rare, and
considered beautiful
are cut and polished
for jewelry
How do minerals form?
• Crystallization
– In hot magma, atoms are not bound in crystal form. As
magma cools the atoms arrange themselves into crystalline
structures forming minerals!
– Happens underground or at the surface in volcanically active
places
• Evaporation/Precipitation
– Atoms can be dissolved in solutions of water. If water
evaporates or changes temperature or gets too many atoms
in it the dissolved atoms may form crystalline
solids…minerals!
– Happens at bottom of bodies of water, especially where there
is volcanically heated hot water dissolving minerals and then
cooling when it touches other water or air.
Diamonds and Graphite
• Why do they have such
different properties?
– Same composition!
– Both minerals!
– Arrangement of atoms
• Why is one common
and the other rare?
• Need to understand the
basic building blocks of
matter and how
minerals form and get
their physical
characteristics
Mineral Characteristics
• Minerals can be identified based on
characteristics such as
– Color, crystal shape, hardness, density
– Streak, fracture vs. cleavage plane, luster,
reaction to acid, magnetism
• These characteristics are caused by
– The type of elements in the mineral
– The arrangement of those elements
How could we make our own
minerals?
• Why is evaporation/precipitation better than
crystallization for us?
• What elements could we dissolve in water?
• What temperature would dissolve the most?
• Will the mineral display crystal form or not?
• What shape crystals do you think will happen?
Color
• Some minerals come in more than 1
color…
Streak
• There are many minerals with the same
color…how do you tell them apart?
No matter what color the
sample of hematite is, it has a
red-brown streak!
Streak is useful for dark, metallic
minerals that are not super hard
What are the two major kinds
of Luster?
• Metallic and non-metallic
• Which has metallic luster?
Crystal Shapes
• Cubic
– Pyrite, galena, halite
• Trigonal
– quartz
• Hexagonal
– beryl
Quartz
Quartz breaks irregularly
• fracture
Mica breaks in flat sheets
• Weak cleavage plane in 1 direction
Cleavage
• Due to weaknesses
planes in the atomic
structure
Mineral ID
1.
2.
3.
4.
5.
Quartz
Feldspar
Feldspar
Calcite
Hornblende/amphi
bole
6. Biotite mica
7. Muscovite mica
8. talc
9. Magnetite
10 Pyrite
11. galena
12. Hematite
13. Graphite
14. Flourite
15. Rose quartz
16. Sulpher
17. Olivine
18. Garnet
Earth’s Geosphere
• 1st semster: atmosphere, hydrosphere, and
exosphere
• 2nd semester: geosphere and exosphere
• Densest part of planet, materials solid at surface
temperatures including rocks and minerals
• Earth is a big rocky metallic planet with a thin film
of life, water and air
• 3 major compositional layers formed through
differentiation
– Core, mantle, crust
– Focus of this unit is on crust
• Composed mostly of just 8 elements
• Diamond: each carbon bonded to 4 other carbons
• Sheets where each carbon is bonded to 3 carbons in hexagon
shape. Sheets weekly bonded together
• How does this impact the characteristics of the mineral?
• http://www.youtube.com/watch?v=Jd9C
40Svt5g