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