Download Minerals

Atomic Structure and Minerals
Basic Structure of Atoms
Atoms
• Smallest particles of matter
• Have all the characteristics of an element
Nucleus – central part of an atom that
contains
• _________ – positive electrical charges
• _________ – neutral electrical charges
Energy levels, or shells
• Surround nucleus
• Contain _________ –
negative electrical
charges
Atomic Bonding and Isotopes
Bonding of atoms
• Forms a compound with two or more elements
• Ions are atoms that gain or lose electrons
Atomic number is the number of protons in an
atom's nucleus
_________
• Have varying number of _________
Isotopes
• Have different mass numbers – the sum of the
neutrons plus protons
• Many isotopes are radioactive and emit energy
and particles
• C, O, U, Ar, K, and Pb are some of the most
common isotopes used in geologic
investigations.
Periodic Table of the elements
Average Abundances for the
____________
Hydrogen is most
abundant
Helium is second
most abundant
04.10.b3
Average Abundances for the
____________ Oxygen second
Magnesium is
abundant metal
04.10.b2
abundant element
Silicon third most
abundant element
Iron most
(abundant) and
nickel in core
Sulfur abundant in
core
Average Abundances in
_____________ Oxygen is most
abundant element
Some
abundant
metals
Silicon is second most
abundant; aluminum
is third
04.10.b1
Iron is most abundant
transition metal
Elements in the Earth’s Crust
• The eight elements that compose most rockforming minerals are oxygen (O), silicon (Si),
aluminum (Al), iron (Fe), calcium (Ca), sodium
(Na), potassium (K), and magnesium (Mg)
• Most abundant atoms in Earth's crust are oxygen
(46.6% by weight) and silicon (27.7% by weight)
How Atoms Bond Together
Sharing
Loaning
Free flow
Metallic bond
Covalent
bond
Stick
together
Intermolecular
force
Ionic bond
04.12.a
How Are Atoms Arranged in a
Mineral?
04.04.c1-3
Cubic
Tetrahedron
Octahedron
Definition of a Mineral
Definition of a mineral
• _______
• _________
• _________
• Possess an orderly internal structure of atoms
• Have a ________ chemical composition
__________ - lacks an orderly internal
structure
Mineraloid
Small openings
Large openings
Openings of different sizes allows the material to flow.
Physical properties of minerals
•
•
•
•
•
•
Crystal form
Luster
Color
Streak
Hardness
Cleavage
• Fracture
• Specific gravity
• Other properties
•
•
•
•
Taste
Smell
Elasticity
Malleability
Crystal Form
• Generally reflects
internal atomic
arrangement
• Typically manifests
best when crystals
have lots of room to
grow.
What Controls a Crystal’s Shape?
Internal structure of halite
Halite (NaCl)
Sizes and
packing
of atoms
04.04.a
Crystal Lattice
Orderly arrangement of
atoms
04.04.b
Repeating
pattern
Crystal Form
Luster
Metallic
Non-metallic
Color
Streak
Hardness
Bonds with Same Strength
Mineral can break along
three sets of planes without
passing through an atom
04.05.b
Mineral breaks through
the lattice in nearly any
direction so it will fracture
Cleavage
Atomic Scale of Mineral Cleavage
Brown atoms bonded with blue
atoms into flat sheets (strong bonds)
Sheets joined by long bonds
between sheets (break
along weakest bonds)
Cleave into sheets
04.05.a
F
r
a
c
t
u
r
e
Special Properties
• Other properties
•
•
•
•
Feel (Talc, Chlorite)
Magnetism (Magnetite)
Double Refraction (Calcite)
Reaction to hydrochloric acid (Calcite)
Building Rocks
• A few dozen minerals are called the rockforming minerals
• These minerals can be grouped according to
their elemental makeup.
Mineral Groups
• _________
• Non-silicates
– ___________ (Limestones)
– Oxides
– Sulfides
– Native Metals– Elements
– Sulfates
Silicates
• Composed of _________________
• Crystallize from molten material
• Minerals are divided by how the silica
tetrahedra are arranged.
The silicate (SiO4)-4 molecule
Silicate Minerals
Silicate
tetrahedron
Tetrahedra
bond
together
and with
other
elements
04.07.b
Rock-forming silicates
• Groups based upon tetrahedral arrangement
• Olivine – independent tetrahedra
• Pyroxene group – tetrahedra are arranged in chains
• Amphibole group – tetrahedra are arranged in
double chains
Independent Tetrahedra
04.07.c
Olivine
Tetrahedra bond to
other elements, not
other tetrahedra
Single Chains
Tetrahedra bond
together to form
single chains
Pyroxene
04.07.c
Double Chains
Tetrahedra bond
to form double
chains
04.07.c
Amphibole
Rock-forming silicates
• Micas – tetrahedra are arranged in sheets
• Two types of mica are biotite (dark) and
muscovite (light)
• Feldspars - Three-dimensional network of
tetrahedra
• Two types of feldspar are Orthoclase and Plagioclase
• Feldspars are the most plentiful mineral group
• Quartz – three-dimensional network of tetrahedra
Sheet Silicates
Mica
04.07.c
Frameworks
Tetrahedra bonded together
and with other elements
in 3D framework
Quartz
Feldspar
04.07.c