I. MINERALS

A. Definition:

1. Naturally occurring

2. Inorganic

3. Solid

4. Crystalline

1. specific chemical composition
2. regular, repeating atomic arrangement

B. Chemical Composition - specific ratio of chemical elements

1. Components

1. protons - positive (+) electrical charge, defining characteristic of a chemical element
2. neutrons - no electrical charge
3. electrons - negative (-) electrical charge

2. Structure - in simplest case (equilibrium) #protons=#neutrons=#electrons

1. nucleus - central core of the atom which contains all of the mass/weight of the atom - all of the protons and neutrons - positive electrical charge
2. electron cloud or electron shells - made of electrons - no mass/weight - negative charge

3. Characteristics of a chemical element

1. atomic number - # of protons,

• defining property of an element,
• gives the name/identity of the element,
• this number is unique to each element

4. Common elements in rocks:

• Si, Al, O, Ca, Mg, Fe, Na, K

5. Variations

1. normal equilibrium - #protons=#neutrons=#electrons
2. ion - #protons equals #neutrons, but is not equal to #electrons (has some electrical charge)
3. isotope - #protons is not equal to #neutrons

C. Crystal structure - regular repeating atomic arrangement

1. silicate structure (Fig. 2.10) - SiO4 tetrahedron

1. isolated tetrahedra
2. single chain
3. double chain
4. sheet
5. 3-D framework

2. silicate minerals

1. isolated tetrahedra -olivine (Fe, Mg)
2. single chain - pyroxene (Fe, Mg)
3. double chain - amphibole (Fe, Mg, Ca)
4. sheet - mica; biotite (Fe, Mg) or muscovite (K)
5. 3-D framework - Feldspar (Ca, NA, K); Quartz (SiO2)

4. Non-silicate minerals

1. calcite (CaCO₃)
2. halite (NaCl)

D. Physical properties

1. luster
2. color
3. crystal shape
4. cleavage
5. fracture
6. hardness
7. specific gravity
8. other (fizz, magnetism, double refraction...)