minerals chapter 2earth materials— minerals and rocks 9/13
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MineralsChapter Chapter 2Earth 2Earth Materials—Materials—Minerals Minerals and Rocksand 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 – SiO2composed 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, gascomposed 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 protonsThis determines the name of the element.
• Atomic mass number is thenumber 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
• 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
Atomic Bonding
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: SiO2
Ratio: 1: 2
Quartz consists of 1 silicon atom for every 2 oxygen atoms
– Potassium Feldsparconsists of 1 potassium, 1 aluminum, and 3 silicon for every 8 oxygen atoms
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
Colorhow 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 hardnessarranged from 1 to 10
• Hardness is a mineral’s resistance to abrasion or being scratched
Streak testcolor 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 LamellaePotassium Feldspar
• StriationsPlagioclase Feldspar
Unique taste, odorhalite 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
Pyroxene-
amphibolebiotite
mica
olivine
Nonferromagnesian Silicates
Quartz Potassium feldspar
Plagioclase feldspar Muscovite
Other Mineral Groups
• Carbonates contain carbonate ion CO3 (CaCO3) calcite
Oxides (Fe2O3) MagnetiteHalides ( NaCl) HaliteSulfides (PbS) Galena