EAR 105 - Exam 2

What are the types of minerals?

Mineral Types  

- There are more than 4,000 known minerals  

- Only a dozen are the main ones making up the Earth.  

- Called the Common rock-forming minerals (a rock is made of 1 or more minerals)  - Of these minerals only about 8 main elements are needed.  

- Silicon (Si) Oxygen (O) Aluminum (Al) Iron (Fe) Magnesium (Mg) Calcium (Ca) Sodium (Na) Potassium (K)  - So much of the solid Earth is made of just 8 main elements. In fact, ignoring Earths crust most  

of solid Earth is made of just Si, O, Fe, and Mg!!  

Identification of Minerals  

- Definition of a mineral  

- Natural  

- Inorganic  

- Solid  

- Possess an orderly internal structure of atoms. Have a definite chemical composition.  - Minerals - result of atoms joining together via chemical bonds producing specific internal  

structure.  

Composed of feldspar and are silica rich.

- It is the nature of the atoms and the strength of the chemical bonds that determine  

many of the mineral’s physical and chemical properties.  

- Crystal Shape or Habitat  

- Optical Properties:  

- Luster  

- Ability to transmit light  

- Color  

- Streak

EAR 105 - Exam 2

- Luster  

- the appearance or quality of light reflected from the surface of a mineral.  - Pyrite: Metallic Luster  

- Quartz: Vitreous (glassy) luster  

- Feldspar: Dull luster  

- Streak  

- defined as the color of the mineral in powder form. More accurate than regular color.  - Hematite has a reddish brown streak.  

- Sphalerite has a light yellow streak.  

- Color  

- (not its streak) is the first thing one notices about a mineral. It is normally NOT a great  physical property to rely on.  

Is felsic rocks and mafic rocks are the same?

- Mineral Strength  

- Determined by: Tenacity, Hardness, Cleavage, Fracture  

- Moh’s scale of Mineral hardness (from soft to hard)  

- Talc, Gypsum, Calcite, Flourite, Apatite, Orthoclase, Quartz, Topaz, Corundum, Diamond.  - Igneous Rocks  

- They are “born of fire”. In other words, they were once molten and upon cooling, the  Don't forget about the age old question of What are the abyssal hills?

magma (molten rock) crystallized into solid rock.  

- Igneous rocks may form deep inside the Earth (intrusive) or at the Earth’s surface  

(extrusive) -- e.g. when a volcano erupts.  

- How do Minerals form?

EAR 105 - Exam 2

- Crystallization is the process of formation of solid crystals precipitating from a solution,  melt or more rarely deposited directly from a gas.  We also discuss several other topics like Who are the big three met to discuss how they were going to wrap up WWII?

- Different minerals crystallize at different temperatures (and under different chemical  conditions) from very hot liquids.  

- How do rocks melt?  

- 1) Heating - obvious, but not most important cause of melting  

- 2) Pressure - especially decompression  

- 3) Water - flux melting (lowers solidus)  

- Classifying Igneous Rocks  

- Granite - intrusive  

- Granite is a coarse to medium-grained rock that forms from the cooling of magma  deep within the Earth (it is an intrusive rock).  If you want to learn more check out What is a biological molecules?

- Rhyolite – extrusive  

- Rhyolite is a fine-grained rock that forms near the surface of the Earth – rapid  

cooling (it is an extrusive rock).  

- Gabbro - intrusive  

- Gabbro is a coarse-grained rock, high in iron & Mg-bearing minerals (pyroxene and  olivine), and Ca-rich feldspar (plagioclase). The rock is dark, denser than granite,  Don't forget about the age old question of Who is Francis Ford Coppola?

and has no quartz.  If you want to learn more check out where do bacteria come from?
We also discuss several other topics like What are the Policy Implications?

- Basalt - extrusive  

- basalt is the extrusive equivalent of Gabbro. It is difficult to see minerals without a  microscope.

EAR 105 - Exam 2

- Diorite – intermediate intrusive  

- Diorite is similar to ‘granitic rocks’ but is distinguished by absence of visible quartz.  - Comparison of felsic and mafic igneous rocks  

- Felsic rocks - Composed of feldspar and are silica rich  

- Mafic rocks - Composed of magnesium and Fe rich minerals  

- Intermediate igneous rocks  

 Intrusive Extrusive 

 Granodiorite <————-> Rhyodacite  

 Tonalite <————-> Dacite  

 Diorite <————-> Andesite