What is a crystal? How do minerals form? What factors affect the size and shape of crystals? What...
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Transcript of What is a crystal? How do minerals form? What factors affect the size and shape of crystals? What...
What is a crystal?
How do minerals form?
What factors affect the size and shape of crystals?
What are the different crystal shapes?
The 5 characteristics of a mineral
• Natural (found in nature)
• Chemical composition (chemical formula)
• Orderly internal structure of atoms (crystal structure)
• Solid
•Inorganic (never living)
Mineraloid - lacks an orderly internal structure
Unit 4 Crystal Formation
PHENOMENON:What did you observe?
What evidence do you have?
OBJECTS:
.What objects
are interacting?
MOTION /STRUCTURE
Describe the structure that in the model that explains your observations
copper wire and silver nitrate
Salt solutions in 100% and 50% concentrations
Salol cooling and crystalizing
Granite rock crystals
Graphite and diamonds
Crystal models and crystals samples in well plate
Part A: Making (silver) Crystals
http://www.youtube.com/watch?v=bJDeoah-Cd0 snowflake crystals
Silver nitrate ‘crystals’pic from phone
• Although not flat surfaces,
the silver
atoms arrange
in a regular repeating
pattern
Definition ofcrystal
Part B: Concentration and Crystal Formation
1. Ions (such as salt or calcium) are dissolved in water.
2. The water EVAPORATES, and the ions form minerals
such as halite, calcite, gypsum, limestone.
http://www.classzone.com/books/earth_science/terc/content/investigations/es0506/es0506page09.cfm
Part C: Crystal and Spacehttp://www.youtube.com/watch?v=HeiMfLmJtzk Mexico's Cueva de los Cristales
(Cave of Crystals) contains some of the world's largest known natural crystals—translucent beams of gypsum as long as 36 feet (11 m). Volcanic activity 26 million years ago created Naica mountain and filled it with high-temperature anhydrite gypsum. When magma underneath the mountain cooled and the temperature dropped, the gypsum that had been dissolved for millions of years began to be deposited in the caves in the form of huge selenite gypsum crystals.
100% concentration
25% concentration
100% concentration
25% concentration
Draw Particle diagrams to show (model) how the crystals formed out of a solution
Salt dissolved in water 25% salt solution salt arranged into 100% concentration crystals
Water salt
White Board Session review
• WB is neat, organized, readable• All members of the group are prepared to explain a
part of the WB• All group members are prepared to answer
questions about the WB• Address questions and answers to the entire class• No judgment statements –ask good questions• It’s okay to make mistakes –that’s how we learn• Be respectful of the presenters.• Every student is responsible for all the information
learned from the discussion
Factors that determine crystal size:
http://www.classzone.com/books/earth_science/terc/content/investigations/es0506/es0506page01.cfm?chapter_no=05ES0506
ConcentrationSpace
Time / rate
Outside inside
Part E: Observe crystals
Under a stereoscope, compare the size of the crystals for 3 magma rocks
Granite Basalt Obsidian
The Magma Process: (pg.97)
• Molten (liquid) rock in a magma
chamberAt, near or under earth’s surface, rises
• The magma begins to COOL. The atoms, ions and molecules combine to form various mineral compounds.
• The molecules arrange into an orderly repeating pattern to form CRYSTALS.
http://www.youtube.com/watch?v=1I5Qc73o5Vk bismuth
quartz
Rate / Time
• The RATE at which the molten magma cools determines the crystal size.
• Predict:
If the magma cools at a s-l-o-w-l-y
(under the surface taking hundreds of years)
then the crystals will be…
well-formed
granite
• If the magma cools quickly (weeks) the crystals will be small / microscopic / not well-formed
(Look at basalt with a hand lens or scope)
• Predict:
• If the magma cools at a very fast rate, quickly, then the crystals will…. None
example: obsidian a volcanic rock, cools instantly.
so it has no crystal structure, but a glass-like structure
Crystallization of Salol Lab
Slow cooling and crystalizing
Quick cooling and crystalizing
________: clear, whitish, transparent
_______________: pink, salmon-colored
___________________: black, gray, dull
________________: black, shiny
quartz
Feldspar (potassium)
Hornblende (amphibole)
Mica - biotite
• Granite contains 3-4 main minerals.
Part E: Rate of Cooling and Size of crystals in Granite
Each mineral melts / crystallizes at its own temperature between 1300ºC and 500ºC
500°C
Rank the order in which the minerals in granite will crystallize.
• First to cool and crystallize ___________• 2nd to crystallize ___________________• 3rd to crystallize ___________________
• Last to crystallize _________________
Hornblende (amphibole)
Feldspar (potassium) - pink
quartz
So. . . Quartz is the LAST to crystallize, so it is usually shapeless.
Biotite mica
The kind of mineral that is formed depends on…
1. Which elements are present when it forms
2. The amount of an each element present.
* The same magma chamber can form different minerals.
Bellwork1. What is the #1 most abundant element in
the Earth’s crust.
2. List the five characteristics of a mineral:
3. What is the hardest and softest mineral on the Moh’s Scale of Hardness?
4. Define a crystal:
5. How does a fast rate of cooling affect the size of
crystals? Slow rate?
ConcentrationSpaceTime / rate
Temperature
Pressure
Where do diamonds form?
Factors that affect the size and shape of crystals
The Pressure Process:
1. Rock or mineral is exposed to extremely high pressures and temperatures, and the minerals begin to break down.
2. As pressure and temperature increase, the molecules RE-FORM into new minerals!
http://www.classzone.com/books/earth_science/terc/content/investigations/es0506/es0506page09.cfm
At what temperature and depth does graphite exist?
Temp:
Pressure:
At what temperature and pressure do diamonds form?
Temp:
Pressure:
Upper mantle
Compare the properties of a diamond and graphite
Color
Luster
Hardness
Cleavage
Crystal structure
Graphite and diamonds are BOTH made of just CARBON atoms
Make a particle diagram of the atoms
graphite diamond
• It takes Gemesis Diamond Co. four days to grow a diamond of an average size of 2.5 carats. The process begins by placing a microscopic diamond grain into a 4,000-pound machine about the size of a kitchen oven. Under hundreds of thousands of pounds of pressure and at temperatures as high as 2,700 °F, the nugget grows, one atom at a time.
• The Gemesis process mimics a diamond's development deep underground. Apollo Diamond, based near Boston, takes a different tack, imitating the way diamonds are made in space. Through chemical vapor deposition, Apollo's process pumps gas into a chamber that essentially rains carbon and forms a diamond nugget from a "seed" within two to four weeks time.
• https://www.youtube.com/watch?v=48NoIICJ2CQGenisis diamonds
Synthetic, man-made diamonds
http://channel.nationalgeographic.com/channel/videos/man-made-diamonds/Synthetic Diamonds
Polymorphs. Minerals which have the same chemical make-up, but different crystal structures
Both diamond and graphite contain only carbon atoms.
Part F: Crystal Shapes
(page 99)
Crystal:
the orderly arrangement of the ions, atoms and molecules that determines the shape of each mineral’s crystals.
Potassium nitrate crystals
Salt crystals
http://www.classzone.com/books/earth_science/terc/content/investigations/es0506/es0506page05.cfm
Part F: Crystal Shape Activity
Paper model letter
Crystal name
Example Mineralname
Traysample
1
2
3
4
5
6
Use table on page 99 in your text book
Look at the crystal samples in the trays under the stereoscopes.
Match them to the crystal models.
A
C
F
D
B
E
Cubic
Tetragonal
Hexagonal
Orthorhombic
Monoclinic
triclinic
Halite
(Salt)
Zircon
Emerald
Topaz
Sulfur
Gypsum
Mica
turquoise
Graphing in WB’s
Factors that affect crystal growth:• Concentration• Space• Time to cool or
Rate of cooling• Temperature• Pressure
Select TWO factors and construct two graphs that show the relationship between them and crystal size and shape.
Example:
Low concentration of material high
A lot of large,well-formedcrystals
Few, shapeless crystals
If….Crystals had enough SPACE to form