ELEMENTS AND MINERALS

I have been to the end of the waters.I have been to the end of the sky.I have been to the end of the mountains.I have found none that are not my friends.

Navajo

MineralsDanny M. Vaughn,

Ph.D., CMS

What is a Mineral?

• Naturally occurring.• Inorganic solid.• Specific chemical composition.• Definite internal structure.• Composed of one or more elements.

Most minerals are compounds.

The Structure of the Atom

• Protons (+)• Neutrons (0)• Electrons (–)

Smallest particles of an element retaining its chemical properties.*

* A property is a distinguishing characteristic.


• Atomic number= Number of protons= Element name

• Atomic Mass= Number of protons

• + neutrons• Isotopes

Circles represent energy levels (shells)


• Atomic number= Number of protonsElement Name

• Atomic massNumber of

protons + neutrons w/in the nucleus.

Chemical stability usually requires eight electrons in the outermost energy level (Octet Rule).

Atoms w/ 1-2 electrons in the outer level tend to give up the electrons.Atoms w/ 3-5 electrons tend to share electrons.Atoms w/ 6-7 electrons tend to acquire electrons.

Periodic Table of the Elements

Isotope – when the number of neutrons ≠ protons. An example:

Oxygen – 816O

The subscript is the atomic number.The superscript is the atomic mass (8 protons + 8 neutrons).

Oxygen – 818O is an isotope; 10 neutrons.

The nuclei of some isotopes break down spontaneously emitting (heat) particles making them radioactive.

Absolute dating using isotopes:Uranium 235 – 92

235UCarbon 14 – 6

14C

How Atoms Bond

Types of bonding

• Ionic• Covalent• Metallic• Intermolecul

ar

Atoms gain or lose electrons, becoming negatively charged

anions or positively charged cations that attract each other combining to form a mineral

compound.

+ -Factors determining whichatoms bond:• How does an atom achieve chemical stability (OctantRule)?• By transferring or sharing electrons to fill the outer energy levels.• Will the compound be electrically neutral?

How Atoms Bond

Types of bonding

• Ionic• Covalent• Metallic• Intermolecula

r

Sharing of electrons between similar atoms.

• Occurs with atoms containing 3-5 electrons in the outer energy level which tend to share electrons.• Generally the strongest bond.

When the outer energy level is already filled with 8 electrons, the element is stable and termed inert since it does not require a gain, loss, or sharing of electrons.

How Atoms Bond

Types of bonding

• Ionic• Covalent• Metallic• Intermolecul

ar

• Electron cloud is attracted to a close-packed, positively charged nuclei forming a metallic bond.• Efficient conductors due to electron movement.

Silver

How Atoms Bond

Types of bonding

• Ionic• Covalent• Metallic• Intermolecu

lar

Weak attraction between molecules (e.g. H2O & NaCl) due to an uneven

distribution of electrons breaks down NaCl in water.

Strong covalent bond

Sodium

Chlorine

Mineral StructureAtoms in silica (SiO2) magnified

1,000,000x

Mineral CompositionMajor Elements of the

Earth’s Crust

Mineral CompositionMajor Elements of the

Entire Earth

Mineral FormationThe type of mineral formed, its spatial extent, geometry, & how it forms are a function of:

• The abundance of elements.• The size & charges of the atoms & ions.• Available space to grow.• Temperature & pressure during formation.

• Compositional variations result when ions of similar size & change substitute for each other (Fe2+ & Mg 2+).

• Minerals with the same chemical composition, but different geometries are termed: polymorphs.

Silence has so much meaning,

Yurok

Identifying Minerals

• Color • Luster• Streak • Hardness• Cleavage • Fracture• Smell • Taste• Effervescence •

Crystal form• Density •

Laboratory tests• Composition & crystal structure (geometric shape*) give a unique combination of chemical and physical properties used in identification.

* Internal arrangement of ions & atoms into a latticework.


• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Effervescenc

e• Crystal form• Density• Laboratory

tests

Tourmaline (Elbaite)




tests

Silver




tests

Hematite




tests




tests

Biotite




tests

Quartz




tests

Halite


• Color• Luster• Streak• Hardness• Cleavage• Fracture• Smell• Taste• Effervesce

nce• Crystal form• Density• Laboratory

tests

Calcite



e• Crystal

form• Density• Laboratory

tests

Stibnite




tests

Galena w/Pyrite & Quartz




tests

Rock-Forming Minerals

SilicatesQuartz (SiO2)Potassium Orthoclase (KAlSi3O8)Albite NaAlSi3O8

[1]

Anorthite CaAl2Si2O8[1]

Olivene (Mg,Fe)2SiO4

Hornblende Ca2(Mg, Fe, Al)5 (Al, Si)8O22(OH)2

Muscovite (mica) KAl2(AlSi3O10)(F, OH)2

Biotite (mica) K(Mg, Fe)3AlSi3O10(F, OH)2

http://en.wikipedia.org/wiki/Sodium

Silicates

Based on the silicon-oxygen tetrahedron

Make up 90% by Weight of Earth’s Crust

• Since the net charge is -4, the structure is not a mineral.• All minerals are electronically neutral.

Types of Silicates

• Independent Tetrahedra• Single chains• Double chains• Sheets• Framework

Olivine

Neutrality occurs when eitheroxygen ions are shared, or when positive ions bond.

Types of Silicates

• Independent tetrahedra• Single chains• Double chains• Sheets• Framework

Pyroxene

Types of Silicates


Amphibole (Hornblende)

Types of Silicates


Muscovite

Types of Silicates

• Independent tetrahedra

• Single chains• Double chains• Sheets• Framework

Quartz

Non-silicate mineral groupsCarbonates - CaO3 complex. e.g., calcite

(CaCO3), dolomite (MgCa(CO3)2). Oxides – Oxygen + metallics. e.g., hematite

(Fe2O3), magnetite (Fe3O4).Sulfur can accept or give up electrons (6 in

outer energy level).Sulfides (accepts electrons) - e.g., pyrite

(FeS2), galena (PbS).Sulfates (gives up electrons, bonds w/ Oxygen

to form SO4) - e.g., gypsum (CaSO4).Native elements - e.g., gold (Au), silver (Ag),

diamond (C), platinum (Pt).

Rock-Forming Minerals

Gemstones

Precious or semi-precious minerals with appealing color, luster, or crystal form

that can be cut and polished for ornamental purposes.

• Amethyst - a variety of quartz• Amazonite - alkaline feldspar• Corundum, sapphire, & ruby • aluminum oxides (Al2O3)

• Diamond - carbon Sapphire

Minerals as Clues to the Past

Minerals that form under specific geological conditions can provide

clues to the past.

Stishovite: a polymorph of quartz forms from intense heat & pressure).

ELEMENTS AND MINERALS

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