Download What is a mineral?

Chapter
Minerals
2Earth
Materials—
Minerals
and Rocks
9/13
Earth Materials – Minerals
• Minerals are the basic
units that make up most of
Earth’s inorganic
materials
• Minerals have many
essential uses
Can you name a few?
What is a mineral?
What is a mineral?
• 1. It is formed naturally
What is a mineral?
• 1. It is formed naturally
• 2. It has a crystalline structure
What is a mineral?
• 1. It is formed naturally
• 2. It has a crystalline structure
• 3. It is solid
What is a mineral?
•
•
•
•
1. It is formed naturally
2. It has a crystalline structure
3. It is solid
4. It has a narrowly defined
chemical composition
What is a mineral?
•
•
•
•
1. It is formed naturally
2. It has a crystalline structure
3. It is solid
4. It has a narrowly defined
chemical composition
• 5. It has characteristic
physical properties
What is a mineral?
•
•
•
•
1. It is formed naturally
2. It has a crystalline structure
3. It is solid
4. It has a narrowly defined
chemical composition
• 5. It has characteristic
physical properties
• 6. It is inorganic
-- never living
Minerals
• Chemical composition:
• composed of elements
Quartz – SiO2
composed of one silicon atom and two
oxygen atoms
• Distinct Properties: color, luster,
hardness, breakage, streak, taste, odor,
magnetic, surface features, reactive with
acid
Matter and Its Composition
• Every substance on earth is composed
of “matter”
• Matter has mass and volume
– (occupies space)
solid, liquid, gas
composed of elements
• Elements are chemical substances
•
cannot be broken down chemically
•
composed of atoms
Atoms
• smallest particle that retains the
nature of the element
Nucleus contains particles
protons: +
neutrons: no charge
Electrons travel around the nucleus
electrons: --
Structure of an Atom
• The dense
nucleus of an
atom
– consisting of
protons and
neutrons
– is surrounded
by a cloud of
orbiting
electrons
Particles in nucleus
• Atomic number: the number of protons
This determines the name of the
element.
• Atomic mass number is the
number of protons + number of neutrons
The number of neutrons in an atom
– may vary without changing the name of the
element
When neutrons vary
• Isotopes of the same element are formed
Isotopes have the same atomic number
• Isotopes have different atomic mass
numbers
• Isotopes of the same element behave the
same chemically
• Isotopes are important in
radiometric dating
Carbon Isotopes
• Carbon atoms (with 6 protons)
– have 6 neutrons = Carbon 12 (12C)
– have 7 neutrons = Carbon 13 (13C)
– or have 8 neutrons = Carbon 14 (14C)
– thereby making up three isotopes of
carbon.
Bonding and Compounds
• Bonding: atoms join to other atoms
• Compound bonding of two or more
elements
• Oxygen gas (O2) is an element
• Ice (H2O) is a compound
•
Most minerals are compounds
Atomic Bonding
• Ionic bonds: electrons are donated or
received
Atomic Bonding
• Common types of bonding among atoms
to form minerals:
• Ionic bonds: electrons are donated or
received
Atomic Bonding
• Common types of bonding among atoms
to form minerals:
• Ionic bonds: electrons are donated or
received
• Covalent bonds: electrons are shared
Atomic Bonding
• Common types of bonding among atoms
to form minerals:
• Ionic bonds: electrons are donated or
received
• Covalent bonds: electrons are shared
• Metallic bonds: electrons are located
in a “cloud” around nucleus
Atomic Bonding
• Common types of bonding among atoms
to form minerals:
• Ionic bonds: electrons are donated or
received
• Covalent bonds: electrons are shared
• Metallic bonds: electrons are located
in a “cloud” around nucleus
• Vanderwaals bonds: atoms are weakly
attracted
Ionic Bonding
• Ion: atom that has gained or lost one or
more electrons
It has a negative or positive charge
• Ionic bonding
– attraction between two ions of opposite
charge
Goal: atoms are more stable when outer
electron shell is filled.
Ionic Bonding
halite
Covalent Bonding
• Covalent
bonding
– results from
sharing
electrons
shared electrons
Metallic Bonding
Electrons are loosely arranged in a
“cloud-like” arrangement.
Metals have properties of being good
electrical conductors
Metals are malleable
Minerals—The Building
Blocks of Rocks
Quartz consists of
1 silicon atom for every
2 oxygen atoms
– Potassium Feldspar
consists of
1 potassium, 1
aluminum, and 3
silicon for every
8 oxygen atoms
Quartz: SiO2
Ratio: 1: 2
KAlSi3O8
1: 1: 3: 8
Native Elements
• consist of only one
element.
• They are not
compounds.
gold – formula: Au
diamond – formula: C
Allotropes of carbon
“polymorphs”
Mineral Properties
• controlled by internal arrangement of
atoms
– Chemical composition
– Crystalline structure
Color
how reliable is color to identify a mineral?
Many varieties of quartz
Crystal form
If given enough room to grow freely
– minerals form perfect crystals with
– planar surfaces, called crystal faces
– sharp corners
– straight edges
Moh’s Scale of hardness
arranged from 1 to 10
• Hardness is a mineral’s resistance to
abrasion or being scratched
Streak test
color of a mineral in its powdered form
Breakage
yes, they all break, but some break in
predictable patterns
• Irregular breakage or fracture:
random, smooth, round (conchoidal) with no
geometric shape or parallel flat sides
Breakage
• Cleavage:
• tendency to break in flat surfaces that are
parallel
may have one, two, three, even four pairs of
flat sides, or planes.
Types of mineral cleavage
Surface feature - feldspars
• Exsolution Lamellae
Potassium Feldspar
• Striations
Plagioclase
Feldspar
Unique taste, odor
halite and sulfur
Reaction with dilute hydrochloric acid –
carbonate minerals
Common rock forming
minerals
Rock-Forming Minerals
• Most rocks are solid aggregates of one or
more minerals
• Thousands of minerals occur in rocks,
but most rocks have common rock-forming
minerals
Most rock-forming minerals are silicates,
but other groups are important
Silicates
• Silicates are minerals containing silica
– Si and O
• They make up perhaps 95% of Earth’s
crust
– and account for about 1/3 of all known
minerals
• The basic building block of silicates
– is the silicon oxygen tetrahedron
• which consists of one silicon atom
• surrounded by four oxygen atoms
Earth’s crust:
elements by weight %
Types of Silicates
• Silica tetrahedra can be
– isolated units bonded to
other elements
– arranged in chains (single
or double)
– arranged in sheets
– arranged in complex
3D networks
Types of Silicates
• Ferromagnesian silicates (dark)
– contain iron (Fe), magnesium (Mg), or both
olivine, pyroxene, amphibole, biotite
• Nonferromagnesian silicates (light)
contain potassium (K), sodium (Na),
(Ca)calcium
– Quartz, muscovite, feldspar
Ferromagnesian Silicates
• Common ferromagnesian silicates include
olivine
amphibole
Pyroxene-
biotite
mica
Nonferromagnesian Silicates
Quartz
Potassium
feldspar
Plagioclase feldspar
Muscovite
Other Mineral Groups
• Carbonates contain carbonate ion CO3
(CaCO3) calcite
Oxides
(Fe2O3) Magnetite
Halides
( NaCl) Halite
Sulfides
(PbS) Galena