Title: Minerals: Building Blocks of Rocks
1Minerals Building Blocks of Rocks
2Mineral
- A
- naturally occurring,
- inorganic solid with an
- ordered internal structure and a
- narrow range of chemical composition.
3What is a mineral?
4Rock
- A naturally-occurring consolidated mixture of
minerals or mineral-like substances.
5Atoms
- A rigid sphere about 1 angstrom (Å) in diameter
(angstrom is 10-10 m). - At the center of an atom is a nucleus which
contains most of the mass of the atom. - Protons (positive charge)
- Neutrons (no charge -- neutral)
- Electrons (negative charge) orbit the nucleus.
6Atoms
- Electrons (E) negative charge, very little mass
- Protons (Z) positive charge, mass 1832x greater
than electron - Neutrons (N) no electric charge, mass 1833x
greater than electron
7Periodic Table
8Atoms
- Atomic Number Number of protons in an atom
- Atomic Mass Sum of the masses of the protons
and neutrons in an atom. - 12C carbon-12 (6 protons and 6 neutrons)
- 13C carbon-13 (6 protons and 7 neutrons)
- 14C carbon-14 (6 protons and 8 neutrons)
- Atoms with the same number of protons and
different numbers of neutrons are called isotopes.
9Atomic structure
Nucleus protons, neutrons
- Electrons orbit
- around the
- nucleus in
- discrete shells.
Fig. 3.2
10C-12
Fig. 3.2
11Electron Cloud
Fig. 3.2
12Energy-level shell the space occupied by
electrons of a particular energy level
- First level (K) 2 electrons
- Second level (L) 8 electrons
- Third level (M) 18 electrons
- Fourth level (N) 32 electrons
Atoms are MOST STABLE when their outer electron
shell is filled.
13Bonding
- Atoms join with other atoms to try to fill their
outer shells. - Two types of bonds
- Ionic bond Formed by the electrical attraction
of ions of opposite charge. 90 of minerals are
formed through ionic bonds. - Covalent bonds Formed by sharing electrons.
Metallic bonds are one type of covalent bond.
Diamonds.
14Ion
- An electrically charged particle composed of an
atom that has either lost or gained electron(s)
to or from another atom. - When an atom loses or gains an electron it is
called an ion. - Positively charged ions (loss of electron) are
called cations. - Negatively charged ions (gain of electron) are
called anions.
15Important ions in minerals
anions charge cations charge
Si 4 K 1 Ca 2 Na 1 Al 3 Mg 2 Fe 2 or 3
O -2
16Ionic Attraction Forms NaCl (Halite)
Fig. 3.4
17Halite
Fig. 3.4
18Atomic Structure of Sodium Chloride (Halite)
19Halite close-up
Fig. 3.6
20Electron Sharing in Diamond
21Carbon Tetrahedron of Diamond
22Network of Carbon Tetrahedra
23Electron Sharing in Diamond
Fig. 3.5
24Crystals
- Crystal Ordered three-dimensional arrays of
atoms in which the basic arrangement is repeated
in all directions.
Fig. 3.8
25How do minerals form?
- Crystallization The growth of a solid from a
gas or liquid whose constituent atoms come
together in the proper chemical proportions and
crystalline arrangement. - When do minerals form?
- Crystallization from a magma
- Crystallization from a pre-existing solid phase
- Precipitation from solution (halite, evaporation)
26Crystals
- Crystal face Boundaries of crystals. Natural
flat (planar) surfaces. External expression of a
minerals internal atomic structure. - Perfect crystal Crystal for which crystal faces
are easily observed. Requires crystallization
under special conditions (e.g., enough room to
grow).
27Quartz Geode
Large space allows larger crystals
28Ionic Radii Determine Packing Geometry
29Graphite
Atomic Structure Crystal Form
After Fig. 3.11
30Diamond
Atomic Structure Crystal Form
After Fig. 3.11
31Polymorphs
- Minerals with the same chemical composition but
different structure. - For example
- diamond (3.5 g/cm3) and graphite (2.1 g/cm3)
- andalusite, kyanite, and sillimanite
32Minerals lots and lots of em
- There are some 3,500 recognized minerals found on
Earth. - However,
- For our purpose, we can focus on about a dozen.
- Groups
- Silicates. Si, O and other elements. Most
abundant mineral group in the Earths crust
(gt75). - Carbonates. Ca, Mg and CO3
- Halides or Salts. NaCl
- Sulfides. Sulfide anion (S2-) and a metallic
cation. - Oxides. O and a metallic cation.
33Chemical classes
34Important mineral groups
Name Important constituents
Silicates Olivine Si, Fe, Mg Pyroxene Si, Fe, Mg,
Ca Amphibole Si, Ca, Mg, Fe, Na, K Micas Si, Al,
K, Fe, Mg Feldspars Si, Al, Ca, Na,
K Carbonates C, Ca, Mg Sulfides Fe, Cu, Zn,
Ni Oxides Fe, Al
35Silica-oxygen tetrahedra
- Building blocks of silicate minerals
- Four oxygens surrounding a silicon ion.
- These tetrahedra combine to make the framework of
the silicates. - Different combinations produce different
structures.
36Silicate IonSiO4 4
Fig. 3.11
37Olivine
Isolated Tetrahedra Silcate (example olivine,
(Mg,Fe)2SiO4)
Fig. 3.11
38Some Silicate Minerals
Mica
Feldspar
Olivine
Pyroxene
Quartz
39Oxides
Hematite, Fe2O3
Corundum, Al2O3
Magnetite, Fe(II)Fe(III)2O4
40Sulfates
Galena, PbS
Gypsum, CaSO42H2O
Pyrite, FeS2
41Carbonates
Dolomite, CaMg(CO3)2
Calcite, CaCO3
42Atomic Structure of Calcium Carbonate(Calcite)
Fig. 3.12
43Important Crustal Minerals
- Feldspar (60 of crust) NaAlSi3O8, CaAl2Si2O8
- Quartz (12 of crust) SiO2
Oxygen (O) 46.3 Silicon (Si) 28.2 Aluminum
(Al) 8.2 Iron (Fe) 5.6 Calcium
(Ca) 4.1 Sodium (Na) 2.4 Potassium
(K) 2.1 Magnesium (Mg) 2.3 Titanium
(Ti) 0.5 Nickel (Ni) trace All others trace
44Important Mantle Minerals
- Olivine (60 of upper mantle) (Mg,Fe)2SiO4
- Clinopyroxene (25 of upper mantle)
Ca(Mg,Fe)Si2O6 - Orthopyroxene (10 of upper mantle) (Mg,Fe)SiO3
- Garnet (5 of upper mantle) X2Y3Si3O12, where
X Ca, Fe, Mg, or Mn, and Y Al, Cr, or Fe
Oxygen (O) 29.5 Silicon (Si) 15.2 Aluminum
(Al) 1.1 Iron (Fe) 34.6 Calcium
(Ca) 1.1 Sodium (Na) 0.6 Potassium
(K) 0.1 Magnesium (Mg) 12.7 Titanium
(Ti) 0.1 Nickel (Ni) 2.4 All others 2.7
45Solid Solution
- Like solutions, minerals can have a range of
compositions. - Continuous range of mineral compositions is
called solid solution. - The range in composition is created because at a
single location in the crystal, several elements
are permitted. - Example
- Olivine (Mg,Fe)2SiO4
- Elements between parentheses indicate a
substitution - End members Fosterite (Mg2SiO4) and Fayalite
(Fe2SiO4).
46IonicRadiusandCharge
Fig. 3.7
47Mineral identification
In hand specimen
- Color
- Crystal form
- Density
- Hardness
- Cleavage
- Streak
48Hardness
- A measure of the ease with which the surface of a
mineral can be scratched.
49Cleavage
- The tendency of a crystal to break along flat,
planar surfaces.
50Cleavage
Atomic Structure of Micas
Fig. 3.17
51Sheety Cleavage of Mica
Fig. 3.17
52Rhomboidal Cleavage of Calcite
Fig. 3.18
53Luster
- The way in which a mineral reflects light.
54Streak
- The color of a fine deposit of mineral dust on an
abrasive surface, such as a tile of unglazed
porcelain (streak plate).
55Hematite
Streak
Fig. 3.20
56Calcite passes the acid test
Fig. 3.16