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Gemstones Exam 1 Cheat Sheet (DRAFT) by

Major/Minor Minerals, Terms & Concepts

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Major Minerals

GEMSTONE
CRYSTAL STRUCTURE
ORGIN & HISTORY
Beryl Be3Al2Si6O18
Hexagonal (6-sided)
Diamond C
Cubic (Octah­edral)
JKJ
Feldspar AlSi3O8
Triclinic or Monoclinic
Garnet X3Y2(SiO4)3
Dodeca­hedron (12-sided)
From "­ger­net­;" Middle English: "dark red"
Gold
Platinum
Quartz
Silver
Topaz
Tourmaline

Minor Gems

 

5 Criteria for Minerals

Naturally Occurring: the mineral has to be formed due to natural processes.
Solid at room temper­ature.
Defined Chemical Formula: follows a proscribed chemical formula within certain except­ions.
Crysta­lline: must possess a repeating crystal lattice.
Inorganic: must be produced abioge­net­ically.

General History of Human Evolution

Paleol­ithic: Appearance of "­tru­e" humans (neand­ert­hals), tool usage, and first jewelry.
Neolithic: New stone age and first agricu­lture.
Chalco­lithic: Copper Age & Beginning of metall­urgy.

EXAM QUESTIONS

Feldspar has...
Two directions of cleavage.
This gemstone has been described as the most colorful gemstone due to its wide range of potential colors and the fact that some gems are multic­olored.
Tourmaline
In the mineral with the chemical formula Al2SiO4(F, OH), where is the water stored?
In hydroxyl groups.
Which of the following gemstones is a cut rock?
Lapis Lazuli
Which of the following particles define the atomic number of an element?
Protons
At which of the following tectonic boundaries would you be most likely to find silver?
Divergent
You have a magma composed only of Calcium (Ca), Potassium (K), Aluminum (Al), Silicon (Si), and Oxygen (O). What feldspar varieties would you expect to form?
KAlSi3O8 and CaAl2Si2O8

Mohs Hardness Scale

 

Gem Anatomy

Terms

Cleavage: Plane of preferred parting along a crystal lattice.
Convection: “The movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which conseq­uently results in transfer of heat.”
Convergent Plate Boundaries: Collis­ional bounda­ries; two plates get pushed together. The denser plate (which is usually the (oldest) oceanic plate) gets pushed under. Volatiles come up to help melt the rock and magma creates mountains.
Cut Rock: Rocks are solid masses of minerals or minera­loids.
Divergent Plate Boundaries: Two plates moving away from each other and they are stretched out. The plates get thinner through time. Some of the magma can then get through and then fill the gaps which creates new crusts.
Exsolution: The process of ordered unmixing of immiscible liquids during crystal formation.
Felsics: (Silica and Feldspar) Formed in contin­ental crust; light and low density; not subducted, usually floats.
Igneous: Rocks which form from molten material (i.e. freeze from liquid rock).
Immiscible: Unable to be mixed.
Index Mineral: Marks stage in metamo­rphism, extent of pressure (i.e. Garnet).
Indicator Mineral: Associated with something that’s really rare (i.e. Garnet & Diamonds).
Intrusive: Igneous rock, cools slowly (i.e. Granite).
Isostasy: The equili­brium between an object and the fluid in which it is suspended (less dense = float higher, more dense = float lower).
Mafic: (Magnesium and Iron) Darker­-co­lored, denser, thinner material that is formed from oceanic crust.
Metamo­rphic: Rocks which form from re-cry­sta­lli­zation at high temper­atures and pressures (not melting).
Mineral: "A solid inorganic substance of natural occurr­enc­e" (specific catego­ry/­che­mical struct­ure).
Molecule: Atoms bonded together as the smallest chemical unit.
Native Element: Naturally occur in an uncombined elemental form with its own mineral structure.
Organic Material: Formed from living organisms (i.e. Amber).
Orogeny: Mountain building event, thickening of crust.
pH: The measure of the "­pow­er" of hydrogen in a solution.
Sedime­ntary: Cold rock processes which involve breaking up existing rocks or biologic processes.
Silicon Tetrah­edral: A "­silicon atom with four surrou­nding oxygen atoms arranged to define the corners of a tetrah­edron (SiO4). "
Slab Pull: “Slab pull is the pulling force exerted by a cold, dense oceanic plate plunging into the mantle due to its own weight.”
Subduction: “The sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate.”
Twinning: Symmet­rical growth of two crystals from the same lattice point.
Ultramafic: Mafic with less silica (darker and denser than mafic)
Unit Cell: How you concep­tualize dividing up a gem. How can you recreate it in a 3D space. Find a common feature. Does it allow you to pick it up and put it anywhere on the same dimension.
Volatiles: Molecules which can be readily vaporized.