Ch_ 2-1Mineral

Chapter 2 Minerals & Rocks
2.1 Mineral definition
2.1.1 Ion substitution
2.1.2 Crystal structure
2.1.3 Mineral classification
2.1.4 Mineral identification
2.2 Rocks
2.2.1 Forming of 3-rock types
2.2.2 Rock cycle
What is a mineral???
2.1 Mineral definition
แร ธาตุหรือสารประกอบอนินทรียท เี่ กิดขึ้นตามธรรมชาติ มีโครงสราง
ภายในที่เปนระเบียบ มีสตู รเคมี และสมบัติอื่นๆ ทีแ่ นนอน หรือ
เปลีย่ นแปลงไดในวงจํากัด (พจนานุกรมศัพทธรณีวิทยา, 2530)
Mineral: A naturally occurring homogeneous solid with a
definite (generally not fixed) chemical composition and a
highly ordered-atomic arrangement usually formed by
inorganic processes
To be a mineral >> naturally formed
solid
specific chemical composition
characteristic crystal structure
Galena-calcite-fluorite
www.boltonmuseums.org.uk/images/geologyimages/mineral_specimen.jpg
http://nevada-outback-gems.com/mineral_information/gold_mineral_info.htm
http://www.free-pictures-photos.com/minerals/mineral-04.jpg
http://www.khyberminerals.com/index_files/agsd.JPG
Is snowflake a mineral?
http://www.its.caltech.edu/~atomic/snowcrystals
Is sugar a mineral?
http://www.made-in-china.com/image/4f0j00eCiaSkMoARrZM/Crystal-Sugar.jpg
http://z.about.com/d/chemistry/1/0/8/R/sugar.jpg
Mineraloid (Noncrystalline minerals):
Natural occurring amorphous substance or minerallike material e.g. natural glass, resins, opal
Amorphous: Substance that lack of internal atoms
arrangement.
Amorphous alloy
Crystalline alloy
http://www.charsdesigns.biz/images/Opal_8.jpg
Fire opal
vibrate.wordpress.com/2007/08/19/fire-opal/
http://mountaincatgeology.files.wordpress.com/2009/04/nev_opal09.jpg
snowflake obsidian
http://www.free-images.org.uk/crystals/03-snowflake-obsidian.htm
moldavite
freakingcat.com/.../Moldavite-Besednice-4.jpg
How can we study minerals???
Characteristics of minerals
Composition:
chemical elements present & their proportion
Crystal structure:
arrangement of atoms of chemical elements
packed together in a mineral
Elements and Atoms
Chemical elements: the most fundamental
substances that matters can be separated by
chemical means.
117 elements in total have been observed (2008)
94 elements occur naturally on Earth
80 elements have stable isotopes, namely all
elements with atomic numbers 1 to 82, except
elements 43 and 61 (technetium and promethium)
Elements with atomic numbers 83 or higher
(Bismuth and above) are unstable and undergo
radioactive decay
The elements from atomic number 83 to 94 have
no stable nuclei, but are nevertheless found in
nature, either surviving as remnants of the
primordial stellar nucleosynthesis which produced
the elements in the solar system, or else produced
as short-lived daughter-isotopes through the
natural decay of uranium and thorium
× Atoms: the smallest subdivision of matter that
retains characteristics of an element.
It contains proton (positive electrical charge) and
neutron (electrical neutral) in the massive nucleus and
surrounded by electron (negative electrical charge)
× Electron mass is 1/1837 that of proton
×
Rutherford's atomic model (1914)
www.daviddarling.info/encyclopedia/R/Rutherfords_experiment_and_atomic_model.html
Neil Bohr’s atomic model (1920)
js082.k12.sd.us/.../atoms/atoms_1.htm
Quantum model of an atom
http://www.splung.com/nuclear/images/atoms10.gif
Shape of s, p & d orbitals
• The
orbitals
are
3dimensional and not precisely
defined
•The charge density falls off
sharply at a certain distance
from the nucleus
• All s-orbitals are spherical
1s < 2s < 3s etc
• All p-orbitals are dumbell
shaped in 3 directions in
space 2p < 3p < 4p
× Atomic number:
number of proton, positive
charge, that equal to
number of electron in
uncharged atom
× Mass number:
summation of proton and
neutron of an element.
Elements
that
contain
different
numbers
of
neutrons called isotopes
http://www.atomicarchive.com/Physics/Images/isotopes.jpg
http://education.jlab.org/glossary/isotope.gif
Ion: atom that lost or gains electron(s) i.e.
cation and anion.
☺ Metal elements tend to give electron and
nonmetal elements tend to receive electron
☺ Energy require for removing first electron
from neutral atom is “first ionisation potential”
☺
What holds atom together???
Chemical bonds
Ionic bond (electrostatic
bond): the attraction between
oppositely
charged
ions.
Resulting in exchanging of
metal atom (forming cation) to
nonmetal atom (forming anion)
Covalent bond: or electron sharing bond is
the strongest chemical bond.
sharing of election when orbitals overlap
Electrons in outer orbital are filled as in stable
inert gas configuration. Hence ionic bonding
also shares some electrons and covalent bond
often contain electrostatic charge, therefore,
the proportion of ionic to covalent character
can be assessed by “Electronegativity”: a
measure of ability of an atom to attract
electron to itself. The greater different of
electronegativity, the more ionic bonding
Metallic bond
atomic nuclei and nonvalence
electron
orbitals
bound
together by the aggregate
electrical charge of a cloud of
valence
electron
that
surrounds the nuclei.
www.daviddarling.info/.../M/metallic_bond.html
Electron(s) belong to no
particular nucleus and freely
mobile through the structure
or even out of it.
Metallic luster, malleable,
electron conductivity.
http://edtech.kku.ac.th/~s48321275011/485050307-2/DSCN2708.jpg
Van der Waals bond
weak dipole attraction that forms by synchronizing of
electrons’ motions in order to avoid each other as
much as possible. This weak dipole, therefore,
induce a similar effect on the adjacent atoms.
www.geo.arizona.edu/xtal/nats101/s04-18.html
Polar bond
Electrons distribution in some
molecule causes charged or
become polar e.g.water H2O.
The side of the molecule with the
hydrogens is slightly positive, the
side with the O is slightly negative.
The complete molecule is neutral.
Water molecule is stable, yet it can
appear to be charged, depending
upons its orientation. This is why
water can dissolve so many things,
e.g. water dissolves NaCl
www.geo.arizona.edu/xtal/nats101/s04-18.html
Hydrogen bond
Hydrogen
bonding
is
very
important. It is a part of most
biological
substances. Covalent
molecules are often terminated by
H atoms. These molecules are held
together by polar bonding of the H
atoms.
www.tutorvista.com/search/egg-protein-content
Example: wood, plastics, silk, candle
wax, DNA.
Egg white is clear because of
hydrogen bonding. But heat it up
and break the bonds, and you end
up with a white gelatinous solid.
Polar and hydrogen bonds are weak
www.geo.arizona.edu/xtal/nats101/s04-18.html
www.chemistryland.com/.../ChangesAssignment.htm
2.1.1 Ionic substitution
Substitution of an ion for another in a crystal
structure
Substitution factors are
– Ionic radius
– Ionic charge
– (Temperature)
Common ionic substitution in geologic materials
S2-
Cl1-
0.184
0.181
O2-
F1-
0.132
Ionic
radius
(nm)
0.136
Ionic charge
K1+
Pb2+
0.133
0.120
Na1+
Ca2+
0.097
0.099
Fe2+
1+
Li
0.074
Mg2+
Fe3+
0.060
0.066
0.064
Al3+
0.050
Si4+
0.042
Common ionic substitution in geology
Mg2+
Ca2+ in calcite-dolomite
Calcite [Ca(CO3)2]
Dolomite [CaMg(CO3)2]
Calcite, Dolomite on Sphalerite - Naica, Mexico
http://www.wrightsrockshop.com/gallery/newacquisitions/quartzgallery2images/calcitesphalerite10609.JPG
Mg2+
Fe2+ in olivine (Mg,Fe)2SiO4
Forsterite (Mg2SiO4)
Fayalite (Fe2SiO4)
http://webmineral.com/specimens/photos/Fayalite.jpg
http://isc.astro.cornell.edu/~spoon/crashcourse/forsterite.fabre_minerals.jpg
Na1+
Ca2+ in plagioclase (Na,Ca)AlSi3O8
http://itc.gsw.edu/faculty/tweiland/albite.jpg
http://www.dadsrockshop.com/rr/rr_labradorite.JPG
How do atoms live in a crystal?
http://
darkwing..uoregon.
http://darkwing
uoregon.edu/
edu/~cashman/
cashman/GEO311/311pages/
GEO311/311pages/L1L1-Intro_pic_files/
Intro_pic_files/image014.
image014.gif
Crystal
o
Homogeneous solid possessing
three-dimensional internal order
o
o
o
long-range
Euhedral crystal
Subhedral crystal
Anhedral crystal
wulfrenite
http://www.amgueddfacymru.ac.uk/geology/mineralogy/media//1/0/1/pyrite1.jpg
Subhedral crystal
http://farm4.static.flickr.com/3253/3043999875_71368848fd_o.jpg
anhedral crystal
http://www.uraniumminerals.com/UTh/S/Samarskite-001a-m.jpg
2.1.2 Crystal structure
geometric pattern that atoms arrange in a solid
Diamond structure
Quartz structure
http://newton.ex.ac.uk/research/qsystems/people/sque/images/diamond-conventional-unit-cell.gif
http://www.rocksandminerals.org/bin/q/l/quartz.gif
Motif
Lattice
Motif
lattice
lattice
lattice
Unit cell
Quartz structure
http://www.quartzpage.de/gen_struct.html
http://www.quartzpage.de/gen_struct.html
Silicon tetrahedron/tetrahedra
http://www.quartzpage.de/gen_struct.html
http://www.briolette.com/images/xf_veracruz_amethyst_matrix1.jpg
http://www.pitt.edu/~cejones/GeoImages/1Minerals/1IgneousMineralz/Quartz/QuartzCrystal.jpg
Crystal structure
geometric pattern that atoms arrange in a solid
http://www.gly.uga.edu/Schroeder/geol3010/galena.gif
http://hyperphysics.phy-astr.gsu.edu/HBASE/Geophys/geopic/galena2.jpg
Graphite VS Diamond Structure
https://www.e-education.psu.edu/earth520/files/earth520/pencils_diamonds.jpg
Crystal systems
Isometric
Hexagonal
Tetragonal
Orthorhombic
Monoclinic
Triclinic
http://gensci.science.swu.ac.th/webrock/images/Crystal%20system1.jpg
Crystallographic axes and angles between axes
Isometric system
Hexagonal system
Tetragonal system
Orthorhombic system
Monoclinic system
Triclinic system
pyrite
Isometric system
a=b=c
α=β=γ= 90°
Hexagonal system
beryl
a1= a2= a3 ≠ c
a1^ a2 ^ a3 =120°
β= 90°
http://encarta.msn.com/encyclopedia_761570052/Crystal_(mineral).html
barite
Orthorhombic system
a≠b≠c
α = γ = β = 90°
idocrase
Tetragonal system
a= b ≠ c
α = γ = β = 90°
http://encarta.msn.com/encyclopedia_761570052/Crystal_(mineral).html
labradorite
gypsum
Monoclinic system
Triclinic system
a≠b≠c
a≠b≠c
α = γ =90°, β > 90°
α ≠ β ≠ γ ≠ 90°
http://encarta.msn.com/encyclopedia_761570052/Crystal_(mineral).html