CHAPTER 3 Earth Materials3.1 Minera

CHAPTER 3
Earth Materials
3.1 Minerals: The Building Blocks of Rocks
Rock - An aggregate of one or more minerals.
Mineral
Naturally occurring.
Inorganic
Solid.
Orderly internal structure (atoms arranged in a definite pattern; crystalline).
Definite chemical composition that may vary within specified limits and written as a formula.
Why study minerals?
Resources.
Building blocks of rocks.
3.2 Minerals: Chemical compounds composed of atoms of various elements
Minerals are chemical compounds composed of atoms of one or more elements.
Chemical compounds change the physical properties.
3.3 Atomic Structure
Building blocks of atoms.
Nucleus - dense central region of the atom
Protons - positively charged; one unit of mass
Neutrons - neutral particles; one unit of mass
Energy-level shells - clouds of electrons at different (discrete) distances from the nucleus.
Electrons - negatively charged; negligible mass (0.00067 AMU); orbit the nucleus
Each shell can contain only a certain number of electrons.
The more electrons, the more energy-level shells
Atomic number = number of protons = number of electrons
Defines the element
Normally an atom of an element is electrically neutral
If electrons are stripped from the atom (or added to the atom), the atom is ionized = ion
Bonding
Elements combine through bonds to form compounds.
Bonding is the result of electrical forces between atoms.
Outermost electrons (outermost energy-level shell) are involved in bonding.
During bonding an atom seeks to fill its outermost energy-level shell (equal to 8).
Electrons involved in bonding are called valence electrons.
Ionic bonds.
One or more valence electrons are transferred from one atom to another."Electron exchange"
Atoms become ions
NaCl is an example (Na+ and Cl-)
Covalent bonds.
One or more valence electrons are shared between atoms "Electron sharing"
Cl2 is an example
Atomic mass = number of protons + number of neutrons
Atoms of the same element commonly have varying number of neutrons in the nucleus, and therefore different atomic masses.
Atoms of the same element with different numbers of neutrons are called isotopes of that element.
Carbon-12 and Carbon-14 are two important isotopes of Carbon.
Carbon-12 has 6 protons and 6 neutrons (most common isotope of Carbon).
Carbon-13 has 6 protons and 7 neutrons.
Carbon-14 has 6 protons and 8 neutrons.
3.4 Structure of Minerals
A mineral is:
An ordered array of atoms.
Chemically bonded.
Forms a crystalline structure.
Each mineral has its own unique crystalline structure.
The crystalline structure is electrically neutral.
Edges have charges.
Polymorphs are different minerals with the same chemical composition.
Different crystalline structures.
Different physical properties.
Diamond and Graphite are good examples.
Both are composed of Carbon atoms.
Diamond - Carbon atoms in 3-D arrays.
Graphite - Carbon atoms in sheets loosely held together electrostatically.
Phase change - change in structure with no change in composition.
3.5 Physical Properties of Minerals
Color.
Usually caused by transition metal elements (iron, copper, etc.).
Sometimes diagnostic; many times not since minor impurities can produce color.
Streak.
Color of a mineral's powder.
One would think it would be the same as the mineral color.
Usually metallic luster minerals have a different streak color. Hematie too.
Luster.
Quality of reflected light.
Adamantine = diamond-like.
Vitreous = glassy.
Pearly.
Greasy.
Oily.
Waxy.
Silky
Earthy.
Dull.
Hardness.
Resistance to scratching or abrasion.
Mohs Hardness Scale.
1. Talc (Texas).
2. Gypsum (Girls).
3. Calcite (Can).
4. Fluorite (Flirt).
5. Apatite (And).
6. Othoclase feldspar (Other).
7. Quartz (Queer).
8. Topaz (Things).
9. Corundum (Can).
10. Diamond (Do.)
Density (specific gravity).
The weight of a mineral divided by an equal volume of water.
A mineral that has a specific gravity of 2.7 is 2.7 times as dense as a equal volume of water.
Gold has a density of 19.3 gm/cm3.
Crystal form (habit).
The shape of an individual crystal or crystals when it can grow unimpeded into an opening in a rock.
dodecahedral, octahedral, hexagonal, cubic, bladed, tabular, fiberous, etc.
Breakage.
How the mineral breaks.
Fracture: random break.
Conchoidal fracture: continuously curving fracture.
Characteristic of quartz and homogeneous minerals.
Cleavage: breaking along crystallographic planes of generally weak chemical bonds.
Special properties.
Magnetism.
Double Refraction.
Two images seen = calcite.
Reaction with acid ("fizzing") calcite.
Taste.
Example: salty.
Smell.
Example: smells like sulfur.
Example: smells like you're near the ocean (salty).
Feel.
Example: soapy or slippery feeling.
3.6 Mineral Groups
There are nearly 4000 minerals.
The rock-forming minerals are most important to geology.
Few dozen of these.
Eight dominant elements (O, Si, Al, Fe, Ca, Na, K, Mg).
A few groups
Silicates - the dominant rock-forming mineral group. Why?
Non-silicates - minor mineral group but economically generally most important.
Native elements
Oxides
Sulfides
Sulfates
Halides
Carbonates
Hydroxides
Phosphates
Silicate structures
(SiO4)-4
Silica tetrahedron.
Silica tetrahedron is an anion which forms the basic building block of the silicates. In silicates, silica tetrahedra are held together by various cations such as Aluminum, Iron, Calcium, Sodium, Potassium, and Magnesium.
Types of silicate structures.
Single tetrahedra in 3-D networks (olivine, feldspar, quartz)
olivine is used as the gemstone peridot
quartz is used for watches (peizeo-electricity), window glass, making silicon chips (anyone like computers?), semi-precious gemstone (amythest)
Single chains (pyroxene group)
spodumene
jadeite
Double chains (amphibole group)
nephrite jade
Sheets (micas and clays)
paint, fine paper coating, kaopectate, bake into bread (Marie), NCR paper, expansive clays, etc.
Silicate minerals.
Most silicates form when rock cools from magma (molten rock).
The temperature and pressure environment, and the chemical composition of the molten rock largely determine the actual minerals which are produced during crystallization. For example:
Olivine and pyroxenes form at higher temperatures.
Quartz forms at lower temperatures.
Some silicates form during metamorphism such as garnet.
Ferromagnesian minerals (mafia)
Have relatively large percentage of Fe and Mg anions
Olivine, pyroxenes (e.g., augite), amphiboles (e.g., hornblende), biotite mica
Olivine contains both Fe and Mg ions that freely substitute for one another depending on the conditions during crystallization.
Non-ferromagnesian minerals (silicic)
Have relatively more Si, Al, Na, K
Quartz, feldspar (both orthoclase and plagioclase), muscovite mica, clays (e.g., kaolinite)
Plagioclase contains both Na and Ca ions that freely substitute for one another depending on the conditions during crystallization.
Non-silicate minerals.
Native elements
gold , silver
copper , silver
graphite , diamond
platinum ,
Oxides
hematite
magnetite
Sulfides
pyrite: used for sulfur; makes poor iron ore
chalcopyrite: primary copper ore mineral in porphyry copper deposits
Carbonates
calcite: used to make cement that is added to sand, gravel, and water to make concrete
dolomite: same
Sulfates
gypsum: used to make wallboard, stucco, plaster, soil amendment
barite: oil drilling additive, X-Rays
Halides
halite: salary; seasoning, food preservative, road salt, document storage
fluorite: steel and aluminum refining
Hydroxides
bauxite (not just one mineral!): aluminum ore rock
Phosphates
apatite (Ca5(PO4)3 (OH, Cl, F); to decieve) teeth

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วัสดุโลกบทที่ 3

3.1 แร่ธาตุ : การสร้างบล็อกของหิน
ร็อค - รวมหนึ่งหรือมากกว่าแร่ธาตุ

แร่ที่เกิดขึ้นตามธรรมชาติ

อนินทรีย์ที่เป็นของแข็ง
โครงสร้างภายในเป็นระเบียบ ( อะตอมการจัดในรูปแบบผลึก ; แน่นอน )
แน่นอนองค์ประกอบทางเคมีที่อาจแตกต่างกันภายในขอบเขตที่กำหนดและเขียนเป็นสูตร
ทำไมศึกษาแร่ธาตุ ?
ทรัพยากร
การสร้างบล็อกของหิน
3.2 แร่ธาตุสารประกอบทางเคมีที่ประกอบด้วยอะตอมของธาตุต่างๆ
แร่ธาตุสารประกอบทางเคมีที่ประกอบด้วยอะตอมของธาตุมากกว่า
สารประกอบทางเคมีการเปลี่ยนแปลงสมบัติทางกายภาพ 3.3 โครงสร้างอะตอม

สร้างบล็อกของอะตอม
นิวเคลียส - ภาคกลางหนาแน่นของอะตอม
โปรตอน - ประจุบวก หนึ่งหน่วยของมวล
- อนุภาคนิวตรอนเป็นกลาง ;หนึ่งหน่วยของมวล
ระดับพลังงานหอย - เมฆอิเล็กตรอนที่แตกต่างกัน ( ไม่ต่อเนื่อง ) ระยะทางจากนิวเคลียส
อิเล็กตรอน - ประจุลบ ; กระจอกมวล ( 0.00067 อามุ ) ; โคจรรอบนิวเคลียส
หอยแต่ละตัวสามารถมีเพียงจำนวนหนึ่งของอิเล็กตรอน
อิเล็กตรอนมากขึ้น เพิ่มระดับพลังงานหอย
= จำนวนโปรตอน = จำนวนอิเล็กตรอนในอะตอม

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