m.a.s.t. convention boxborough, ma - 2009

M.A.S.T. ConventionBoxborough, MA - 2009

Mineral Formation - BackgroundCritical Thinking and Collaborative Learning

Session 76

Presented by Mark D. GreenmanEinstein Fellow, National Science Foundation

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Mark D. Greenman. [email protected] (781) 248-4952

The Magma Chamber

Magma is a homogenized soup of minerals and/or mineral components (this includes elements like Iron (Fe), Aluminum (Al), gold (Au), lead (Pb), Magnesium (Mg), etc. and ions like (SiO4), (SiO3), (AlSi3O8), (CO3), etc). The magma is so hot that individual molecules of these minerals can not form fixed inter-molecular bonds and cations like Al, Fe, Mg, etc. and anions like (SiO4), (SiO3), (CO3), etc. can not maintain intact network structures of bonded cations and ions

Point of Information: The mineral composition of a magma pocket varies. The silicate content is usually between 50 and 70 percent. The more silicate the more viscous is the magma.


The Magma Chamber• As the magma cools these compounds, elements and ions

can begin to form fixed molecular bonds and network structures (they begin to crystallize out of the magma soup).

• Each type of mineral begins this process at a different temperature.

• Each type of mineral ends this process at a different temperature.

• The crystallization process takes place within a specific range of temperatures (too hot and fixed bonds can’t form - too cool and the molecules that make up the mineral can no longer move to join other groups of like molecules).

• The longer the magma stays within this range of temperature the larger the “mineral clumping.”


MineralsA Mineral is: (1) a pure substance† (i.e., has a definite chemical composition with unique physical properties); (2) is in the solid state; (3) is naturally occurring; (4) is free of organic materials.

† The geologist definition of a “pure substance” and the chemist definition are not quite the same. A feldspar sample with a small number of Aluminum sites replaced by a chemically similar element in the anion would still be classified as feldspar by a geologist even though the chemist would not agree that the sample is pure. This allowance for “impurities” gives rise to the variation in colors within a specific mineral and explains why a mineral can have a range of temperatures to crystallize. A truly pure substance crystallizes at a unique single temperature.



Quartz SiO2

Feldspars … (AlSi3O8)

Hornblende… (Si8O22)(OH)2

Mica …(AlSi3O10)(OH)2

Silicate Minerals: By weight, silicon constitutes 28% of the Earth’s crust while Oxygen comprises 47% of the Earth’s crust.

Rule of thumb: Silicate based minerals with cations of Iron (Fe), Magnesium (Mg), or Calcium (Ca) tend to be dark. Those with Aluminum (Al) or Potassium (K) are light.



Galena PbS2

Calcite Ca(CO3)

GypsumCa(SO4)

Corundum Al2O3

Other Important Mineral Groups: Sulfide, sulfate, carbonate, and oxide based minerals.



Gold Au

Diamonds C

SilverAg

Sulfur S

Other Important Mineral Groups: Elements such as gold, silver, diamonds, and sulfur.

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Igneous Rocks - A Mixture of Minerals


Mineral Formation - The ActivityCritical Thinking and Collaborative Learning

Session 76


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Organizing the Classroom

The Team: Choose a captain, a temperature monitor, and 2 scientists. The captain and the 2 scientist pick two minerals to study.

Mineral Formation FoodName Temperature CompositionQuartz 800-700C Fl3

Light Feldspar 1000-800C Sw1(Bs1Fl1)Dark Feldspar 1100-900C C2(Bs1Fl1)Olivine 1200-1100C Sb3Fl1

Corundum 1000-800C Bs1S2

Hematite 800-700C Sb3S2

The Supplies: The captain gets the mineral cards. The temperature monitor gets a stopwatch, 6 spoons, and 6 baggies. The 2 other scientists get between them the 6 bowls filled with the ions.

The Lab Bench: Each scientist and the captain get 2 baggies, 2 mineral cards, and 1 spoon. The ion bowls are placed on the table so they are in easy reach for all members of the team.


Organizing the Team

Final Check: The captain records the names of the minerals assigned to each mineralogist. The captain asks each scientist to read off their minerals’ temperature crystallization range and ion proportions.. Each scientist records this information in their science notebook.





The Magma Cooling Table: The head volcanologist (teacher) places the magma cooling table on the board.


The Experiment Begins

Not a Race: Each mineralogist must listen for the temperature prompts from the temperature monitor. When taking ions ONLY take LEVEL teaspoons of material from the bowls. A science team works cooperatively.





Forming the Minerals: ONLY make your assigned mineral when the temperature is in the appropriate range. Once you have finished making your mineral(s), seal the baggie and mix the ions VERY well.


Analyzing the Data

Q1: Iron and calcium (Sb and C) minerals versus potassium and aluminum (Sw and Bs) minerals - Observe and record differences.





Q2: Comparing the amounts of each kind of mineral.

Q3: Conjecture on reason(s) for differing amounts.

Q4: Conjecture on what 2 things could be changed to result in differing amounts.

Q5: Conjecture on ease of separating ions that make up a mineral.

Q6: Two classification schemes to characterize your minerals into 2 groups.


Thinking Deeply

Q7: Speculate on how the mass per 30 mL cup (density) measure might be a useful quantity.





Q8: Additional observations and conjectures.

Debriefing the ExerciseStrengths and weaknesses


Mineral FormationCritical Thinking and Collaborative Learning

Session 76


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m.a.s.t. convention boxborough, ma - 2009

Documents

mineral composition

mineralsa mineral

specific mineral

type of mineral

mineral clumping

pure substance

magma soup

magma chambermagma