BELL WORK: Define MINERAL: TODAY: Intro to MINERALOGY

EXAMINE EACH SAMPLE Please be careful! Some minerals are very delicate and will break Using as many senses as possible – please completely describe each sample in your notebook for example: “gold and shiny, looks like corn flakes stuck on a rock, sharp edges, heavy..” Write the descriptions as a cheat sheet in case you have to identify them again…

MINERALOGY: BELL WORK – watch the video and tell me what accounts for the color variation in the diamonds. (Remember the chemical formula for diamonds – C ) Diamonds Gems What is a mineral

ATOMS, ELEMENTS & MINERALS PART I – BASIC CHEM REVIEW PART II – CRYSTALLINE STRUCTURES PART III – PHYSICAL PROPERTIES

ATOMS AND ELEMENTS An element is a substance that can not be broken down into others by ordinary chemical reactions An atom is the smallest unit of a substance that retains the properties of that element Composed of 3 types of subatomic particles Protons (positively charged) Neutrons (zero net charge) Electrons (negatively charged) A molecule is the smallest unit of a compound that retains the properties of that substance

ATOMS AND ELEMENTS 92 naturally occurring elements (specific arrangements of atoms) Atomic number = number of protons Mass number = number of protons and neutrons Isotopes – same atoms w/ different number of NEUTRONS but the same number of protons in each atom.

Atomic Structure Protons and neutrons form the nucleus of an atom Represents tiny fraction of the volume at the center of an atom, but nearly all of the mass Electrons constantly move and occupy space around the nucleus in discrete shells or energy levels Shells represent nearly all of the volume of an atom, but only a tiny fraction of the mass Numbers of electrons and protons are equal in a neutral atom Ordinary chemical reactions involve only outermost shell (valence) electrons The most stable configuration for an atom is when each energy level is completely filled.

BELL WORK List the most abundant elements on Earth’s crust in order from most to least.

Composition of Earth’s Crust Common elements Nearly 97% of the atoms in Earth’s crust are represented by the 8 most common elements Minerals have crystalline structures Regular 3-D arrangement of atoms Common mineral types Most minerals are silicates (contain Si and O bonded together) Insert Box 2.3 - Fig. 2A here

ANSWERS O – 46.6 Si – 27.7 Al – 8.1 Fe – 5.0 Ca – 3.6 Na – 2.8 K – 2.6 Mg – 2.1 Other – 1.5 MAKE UP YOUR OWN ACRONYM FOR THESE

WHAT is a CRYSTAL?

Crystalline Substance All atoms are arranged in an orderly, regularly repeating, 3 dimensional pattern.

WHAT is a Mineral? Come up with a definition…. Do you remember the movie last week?

MINERALS Defined as an inorganic, naturally occurring, crystalline structure that is physically and chemically distinctive. Have specific chemical formulas Quartz has twice as many oxygen than silicon atoms. i.e.; Quartz = SiO 2

MINERALS INTRODUCTION Each mineral is: Compositionally and physically distinctive Develops in a particular way Distinguished by a combination of properties A crystalline substance The arrangement of atoms are orderly and regular

MINERALS Defined as an inorganic, naturally occurring, crystalline structure that is physically and chemically distinctive. Have specific chemical formulas Quartz has twice as many oxygen than silicon atoms. i.e.; Quartz = SiO 2

END OF SECTION 1 Read text pages 29 – 33. We will be going over Ions and Crystalline Structures in the next lecture. Start terms in your notebook pg. 53 – they will all be due next week.

Minerals A mineral must meet the following criteria: Crystalline solid Atoms are arranged in a consistent and orderly geometric pattern Forms through natural geological processes Has a specific chemical composition May include some internal compositional variation, such as the solid solution of Ca and Na in plagioclase) Rock-forming minerals Although over 4000 minerals have been identified, only a few hundred are common enough to be generally important to geology (rock-forming minerals) Over 90% of Earth’s crust is composed of minerals from only 5 groups (feldspars, pyroxenes, amphiboles, micas, quartz)

MINERALS NON SILICATES SILICATES NOT ABUNDANT VERY ABUNDANT Halides Carbonates Sulfates Sulfides Oxides Native elements SILICATES VERY ABUNDANT Vary from simple to complex arrangements of Silica

Silica Silicon and oxygen combined Silicon is the 2nd most abundant element on earth so most minerals contain silica. Mineral substances that contain silica are called silicates.

Silicon – Oxygen Tetrahedron 4 oxygen atoms (anions) 1 silicon atom Each corner represents the center of an oxygen atom Basic building block of a silicate mineral

Silicon – Oxygen Tetrahedron Formula SiO4 ‾‾ 4 Silicon has a charge of +4 4 oxygen have 8 negative charges (-2 for each) Can bond with positively charged ions , like Al or Fe (balanced by enough + charged ions) OR w/ other S-O-T’s. So for it to be stable it must share + ions or share oxygen w/ adjacent tetrahedrons (reduce the need for extra + charged ions)

Silicate Structures – Page 39 Sharing of O atoms in tetrahedra The more shared O atoms per tetrahedron, the more complex the silicate structure Isolated tetrahedra (none shared) Chain silicates (2 shared) Double-chain silicates (alternating 2 and 3 shared) Sheet silicates (3 shared) Framework silicates (4 shared)

VIDEO

Isolated Silicate Structures- NEOSILICATES Silicate minerals are structured so that none of the O atoms are shared by tetrahedrons. The isolated silicate structure is bonded by positively charged ions (fig. 2.9) EX: Olivine (Mg,Fe)2SiO4 contains ions of either Fe+2 or Mg+2 for each S-O-T.

Nesosilicates Phenacite-- Be2(SiO4) Willemite-- Zn2(SiO4) Olivine--(Fe, Mg)2(SiO4) Garnet-- A3B2(SiO4)3 Zircon-- Zr(SiO4) Andalusite--Al2 SiO5 Sillimanite-- Al2 SiO5 Kyanite-- Al2SiO5 Topaz-- Al2(SiO4)(F, OH)2 Staurolite-- Fe2Al9O6 (SiO4)4(O, OH)2 Chondrodite--Mg5(SiO4)2(F, OH)2 Datolite--CaB(SiO4)(OH) Sphene--CaTiO(SiO4)

Sorosilicates The sorosilicates are characterized by isolated double silicate tetrahedra that share an oxygen.

Sorosilicates Common Sorosilicate Minerals Hemimorphite-- Zn4(SiO4) Lawsonite--CaAl2(Si2O7)(OH).(H2O) Clinozoisite--Ca2Al3(SiO4)(Si2O7)(OH) Epidote-- Ca2(Al, Fe)(Al2O)(SiO4)(Si2O7)(OH) Idocrase--Ca10 (Mg, Fe) 2Al4(SiO4)5(Si2O7)(OH)7 Prehnite-- Ca2Al2(Si3O10)(OH)2

Chain Silicates Structures form when two tetrahedron’s O is shared w/ adjacent tetrahedrons to form a chain (net –charge)

Single Chain Ionosilicates– PYROXENE GROUP Single chain – Silicon to Oxygen, 1:3, so each mineral in this group incorporates SiO3 -2 in its formula and must be balanced by + ions that holds parallel chains together.

Single chain inosilicates Pyroxene group Diopside - hedenbergite series Diopside - CaMgSi2O6 Hedenbergite - CaFeSi2O6 Augite - (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6 Sodium pyroxene series Jadeite - NaAlSi2O6 Aegirine (Acmite) - NaFe3+Si2O6 Spodumene - LiAlSi2O6

Double chain inosilicates Double Chain – AMPHIBOLE GROUP Two adjacent chains sharing O atoms. Every other tetrahedron shares an O with the adjacent chains tetrahedron.

Double chain inosilicates Amphibole group Anthophyllite - (Mg,Fe)7Si8O22(OH)2 Hornblende - (Ca,Na)23(Mg,Fe,Al)5Si6(Al,Si)2O22(OH)2 Sodium amphibole group Glaucophane - Na2Mg3Al2Si8O22(OH)2 Riebeckite (asbestos) - Na2Fe2+3Fe3+2Si8O22(OH)2 Arfvedsonite - Na3(Fe,Mg)4FeSi8O22(OH)2

Cyclosilicates 3-member ring 4-member ring 6-member ring Benitoite - BaTi(Si3O9) 4-member ring Axinite - (Ca,Fe,Mn)3Al2(BO3)(Si4O12)(OH) 6-member ring Beryl/Emerald - Be3Al2(Si6O18) Cordierite - (Mg,Fe)2Al3(Si5AlO18) Tourmaline - (Na,Ca)(Al,Li,Mg)3-(Al,Fe,Mn)6(Si6O18)(BO3)3(OH)4

Phyllosilicates Sheet Silicates – MICA GROUP Each tetrahedron share three O atoms to form a sheet. + ions that hold sheets together are sandwiched between silicate sheets.

Phyllosilicates Sheet Silicates – MICA GROUP Serpentine group Antigorite - Mg3Si2O5(OH)4 Chrysotile - Mg3Si2O5(OH)4 Clay mineral group Kaolinite - Al2Si2O5(OH)4 Talc - Mg3Si4O10(OH)2 Mica group Biotite - K(Mg,Fe)3(AlSi3O10)(OH)2 Muscovite - KAl2(AlSi3O10)(OH)2 Chlorite group Chlorite - (Mg,Fe)3(Si,Al)4O10(OH)2•(Mg,Fe)3(OH)6

Tectosilicates Framework Silicates – Quartz Group Tectosilicates, or "framework silicates," have a three-dimensional framework of silicate tetrahedra with SiO2 or a 1:2 ratio. All four O ions are shared by adjacent tetrahedrons.

Tectosilicates Tectosilicates, with the exception of the quartz group, are aluminosilicates. Quartz and feldspar silicates are more complex b/c Al substitutes for some of the silicon in some of the tetrahedrons.

Examples Quartz group Feldspar group Quartz - SiO2 Tridymite - SiO2 Alkali-feldspars Potassium-feldspars Microcline - KAlSi3O8 Orthoclase - KAlSi3O8 Plagioclase feldspars Albite - NaAlSi3O8 Oligoclase - (Na,Ca)(Si,Al)4O8 (Na:Ca 4:1)

BONUS POINTS 3-D models of silicate structures made with cardboard up to 5 bonus points!

Q! Explain the importance of the Silicon Oxygen Tetrahedron. A! They are the building block for most common minerals on earth.

Non - Silicate Not abundant in earth DO not contain Silica Still important

Non-silicate Minerals Halides -Contains chlorine, bromine, fluorine, and iodine are combined with one or more metals Carbonates Contain CO3 in their structures (e.g., calcite - CaCO3) Sulfates Contain SO4 in their structures (e.g., gypsum - CaSO4. 2H2O) Sulfides Contain S (but no O) in their structures (e.g., pyrite - FeS2) Oxides Contain O, but not bonded to Si, C or S (e.g., hematite - Fe2O3) Native elements Composed entirely of one element (e.g., diamond - C; gold - Au)

Halides The minerals that make up the halide class form as evaporates – in environments that have chemicals dissolved in solution that evaporates and leave the minerals (precipitates) behind. Minerals of the halide class all have: relative low hardness moderate to high melting points poor conductors of heat and electricity

Carbonates In nature, carbon atoms join with oxygen to form the carbonate ion, CO3. These ions combine with metal cations to form carbonate minerals. The carbonates fall into three groups: the calcite group, the dolomite group and the aragonite group. The copper carbonate minerals azurite and malichite are the only important economic carbonates.

Carbonates Calcite (CaCO3)

Sulfates The basic unit of the sulfate minerals are the SO4 groups. These groups combine with metals to form the sulfate minerals. A large number of minerals belong to this class, but only a few of them are common. The class can be divided into the anhydrous (no water) sulfates and the hydrous (water) and basic sulfates.

Sulfates Gypsum (CaSO4 (+2H2O))

Describe the importance of the non-silicate minerals.

Sulfides The minerals that make up the sulfide class are composed of metal cations (+2 charge) combined with sulfur. The sulfides form an important class of minerals which includes the majority of the ore minerals. They form in environments low in oxygen.

Sulfides Pyrite (FeS2)

Oxides The minerals that make up the oxide class include those in which oxygen is combined with one or more metals. Within the oxide class are several minerals of great economic importance. These include the chief ores of iron, chromium, manganese, tin, and aluminum.

Oxide examples Hematite (Fe2O3) Magnetite is another type of oxide!

Native Elements Minerals that are composed of atoms of a single element are referred to as native elements. Gold group Platinum group iron group Semimetals group

Non- Silicate Minerals Ore minerals Minerals of commercial value Most are non-silicates (primary source of metals) Examples: magnetite and hematite (iron), chalcopyrite (copper), galena (lead), sphalerite (zinc) Must be able to be extracted profitably to be considered current resources Gemstones Prized for their beauty and (often) hardness May be commercially useful Diamond, corundum, garnet, and quartz are used as abrasives

Variations in Mineral Structure and Composition Only a limited # of minerals compositions exist - Random combinations don’t happen Combinations can only form a limited # of crystalline structures Each type of mineral may NOT be compositionally different BUT each type can show different structural variation

FOR EXAMPLE Fe and Mg can interchange to create a range of compositions in Olivine (Fe,Mg)2 SiO4 Pure Mg olivine Mg2SiO4 forms bright green peridot Pure Fe olivine Fe2SiO4 forms jet black fayalite Crystal structures are identical

Olivine Variations Fe2SiO4 Fayalite Mg2SiO4 Peridot

POLYMORPHISM The same chemical composition but different crystalline structures Calcite and Aragonite are both CaCO3 but crystal structures differ b/c of the environment where conditions and processes of formation differ

CaCO3 CALCITE Aragonite

Properties Quiz What is STREAK and how is it used? What is LUSTER? Is mineral color a reliable property for Identification? What is the arrangement and formula for the silicon oxygen tetrahedron? What is silica and Why is silica so important?

Mineral Properties Physical and chemical properties of minerals are closely linked to their atomic structures and compositions Color Visible hue of a mineral Streak Color left behind when mineral is scraped on unglazed porcelain Luster Manner in which light reflects off surface of a mineral Hardness Scratch-resistance Crystal form External geometric form

Mineral Properties Cleavage Fracture Specific gravity Magnetism Breakage along flat planes Fracture Irregular breakage Specific gravity Density relative to that of water Magnetism Attracted to magnet Chemical reaction Calcite fizzes in dilute HCl