Monument ValleyMonument ValleyUnit 1-CO, p.21

Quartz CrystalsQuartz Crystals

Fig. 2-CO, p.22

Vermiculite mine, Libby Montana. Vermiculite mine, Libby Montana. Discovered 1881, its properties make it valuable for packing, Discovered 1881, its properties make it valuable for packing,

insulation and as a soil additive (when heated it expands to insulation and as a soil additive (when heated it expands to form a lightweight, fireproof, inexpensive material). form a lightweight, fireproof, inexpensive material).

Contaminated with asbestos: a mineral that is a known to cause Contaminated with asbestos: a mineral that is a known to cause cancer and lung disease. cancer and lung disease. Fig. 2-1, p.23

What is a mineral? What is a mineral? naturallynaturally occurringoccurring, , inorganicinorganic solidsolid with a with a definitedefinite

chemical compositionchemical composition and a and a crystalline structurecrystalline structure..Fig. 2-2b, p.25

naturally occurringnaturally occurring:: many many minerals can be manufactured minerals can be manufactured (e.g., synthetic diamonds).(e.g., synthetic diamonds).

inorganic:inorganic: do not contain do not contain carbon-hydrogen bonds carbon-hydrogen bonds (organic…plants and animals (organic…plants and animals create most of Earth’s organic create most of Earth’s organic material)…what about coal and material)…what about coal and oil? Shells of marine animals?oil? Shells of marine animals?

solid:solid: all minerals are solids. all minerals are solids.

Is water a mineral? Is ice a Is water a mineral? Is ice a mineral?mineral?

chemical compositionchemical composition and and crystalline structurecrystalline structure covered covered next.next.

Granitic Rock, Bugaboo Mtns, BC Granitic Rock, Bugaboo Mtns, BC CanadaCanada Fig. 2-2a, p.25

Elements,Elements, Atoms, and the Chemical Atoms, and the Chemical Composition of Minerals.Composition of Minerals.

Minerals are the building blocks of rocks, composed of Minerals are the building blocks of rocks, composed of chemical elements.chemical elements.

Element:Element: fundamental component of matter, cannot be broken fundamental component of matter, cannot be broken down by ordinary processes. Most minerals are composed of down by ordinary processes. Most minerals are composed of 2-5 elements.2-5 elements.

Of the 88 naturally occurring elements in Earth’s crust, 8 make Of the 88 naturally occurring elements in Earth’s crust, 8 make up 98% of the crust: O, Si, Al, Fe, Ca, Mg, K and Na (see slide).up 98% of the crust: O, Si, Al, Fe, Ca, Mg, K and Na (see slide).

AtomAtom: basic unit of an element, and it consists of a nucleus (+) : basic unit of an element, and it consists of a nucleus (+) surrounded by electrons (-). The nucleus of composed of surrounded by electrons (-). The nucleus of composed of protons (+) and neutrons (no charge) (see slide). protons (+) and neutrons (no charge) (see slide).

Ion:Ion: positively (cation) or negatively (anion) charged atoms. positively (cation) or negatively (anion) charged atoms. Oxygen is commonly an anion and Earth’s abundant minerals Oxygen is commonly an anion and Earth’s abundant minerals are commonly cations, so form compounds (of elements). Held are commonly cations, so form compounds (of elements). Held together by chemical bonds. together by chemical bonds.

So, minerals are compounds, usually 2-5 essential elements, So, minerals are compounds, usually 2-5 essential elements, expressed as a chemical formula: SiO2 for quartz, contains one expressed as a chemical formula: SiO2 for quartz, contains one silicon (+4) for every two oxygen (-2) atoms. Can you think of silicon (+4) for every two oxygen (-2) atoms. Can you think of an mineral that consists of only one element? an mineral that consists of only one element?

Table 2-1, p.28

The 88 elements The 88 elements that occur naturally that occur naturally in the Earth’s crust in the Earth’s crust can combine many can combine many different ways to different ways to form the more than form the more than 3,500 minerals 3,500 minerals known. However, known. However, the 8 abundant the 8 abundant minerals generally minerals generally combine in only a combine in only a few ways, resulting few ways, resulting in 9 rock-forming in 9 rock-forming minerals (or mineral minerals (or mineral groups) that make groups) that make up most of the up most of the Earth’s crust.Earth’s crust.

Electrons Electrons concentrate in concentrate in layers or shells layers or shells around the around the nucleus of an nucleus of an atom.atom.

Fig. 2-3, p.28

When sodium (Na) and chlorine (Cl) atoms combine, When sodium (Na) and chlorine (Cl) atoms combine, sodium loses one electron, becoming a cation (Na+); sodium loses one electron, becoming a cation (Na+); chlorine gains the electron to become an anion (Cl-). chlorine gains the electron to become an anion (Cl-).

p.26

p.27

Every mineral is a crystal (has a crystalline structure). It means Every mineral is a crystal (has a crystalline structure). It means the atoms are arranged in a the atoms are arranged in a regular, periodically repeated regular, periodically repeated pattern.pattern.

The mineral The mineral halitehalite (common table salt; NaCl) has one Na for (common table salt; NaCl) has one Na for every Cl atom. They alternate in orderly rows and columns that every Cl atom. They alternate in orderly rows and columns that intersect at right angles. This is its crystalline structure. intersect at right angles. This is its crystalline structure.

Unit CellUnit Cell: a small group of atoms, like a brick in a wall, repeats : a small group of atoms, like a brick in a wall, repeats itself over and over. Repeating bricks produce a rectangular itself over and over. Repeating bricks produce a rectangular shaped wall (or some modification of a rectangle), similar to the shaped wall (or some modification of a rectangle), similar to the unit cell in crystals. Halite’s unit cell shown above. unit cell in crystals. Halite’s unit cell shown above. Fig. 2-4, p.29

Orderly Orderly arrangement of arrangement of sodium and sodium and chlorine ions in chlorine ions in halite (shows the halite (shows the unit cell). unit cell). Exploded view.Exploded view.

Fig. 2-4a, p.29

Show ions in Show ions in contact (halite contact (halite crystal). crystal).

Fig. 2-4b, p.29

Shape of well-Shape of well-formed crystal formed crystal determined by determined by the shape of the the shape of the unit cell and the unit cell and the manner in which manner in which the crystal the crystal grows. Stacking grows. Stacking of small cubic of small cubic unit cells could unit cells could produce the produce the cube (top) or cube (top) or octahedron (8-octahedron (8-sided crystal) to sided crystal) to right. Not all unit right. Not all unit cells are cubic. cells are cubic.

Fig. 2-5, p.29

Halite crystals Halite crystals showing crystalline showing crystalline structure from structure from regular repeated regular repeated pattern of unit cells. pattern of unit cells. These crystals These crystals probably grew probably grew during evaporation during evaporation of salty seawater.of salty seawater.

This halite (to right) This halite (to right) shows well-shows well-developed developed crystal crystal facesfaces (flat surface (flat surface that develops if a that develops if a crystal grows freely crystal grows freely in an uncrowded in an uncrowded environment). environment). Fig. 2-4c, p.29

In nature the In nature the growth of crystals is growth of crystals is often impeded by often impeded by adjacent mineral adjacent mineral grains. Minerals grains. Minerals rarely show perfect rarely show perfect development of development of crystal faces. This crystal faces. This is a thin section of is a thin section of granite, showing granite, showing that crystals fit that crystals fit together like a together like a jigsaw puzzle. jigsaw puzzle. Crystals grew Crystals grew around others as around others as molten magma molten magma solidified. solidified.

Fig. 2-6, p.29

Physical Properties of MineralsPhysical Properties of Minerals

How do geologists identify minerals in the field? How do geologists identify minerals in the field? Chemical and crystal structure analysis’ aren’t Chemical and crystal structure analysis’ aren’t practical in the field, so geologists rely on practical in the field, so geologists rely on physical properties to identify minerals, and can physical properties to identify minerals, and can use simple tests to confirm identification. use simple tests to confirm identification.

These physical properties include These physical properties include crystal habit, crystal habit,

cleavage and fracture, hardness, color, luster, cleavage and fracture, hardness, color, luster, specific gravity, streak and a few other specific gravity, streak and a few other properties such as magnetism and reaction to properties such as magnetism and reaction to acid. acid.

Crystal HabitCrystal Habit

Characteristic shape of a mineral, and the manner in Characteristic shape of a mineral, and the manner in which aggregates of crystals grow. If it grows freely, which aggregates of crystals grow. If it grows freely, shape is controlled by arrangement of atoms (like shape is controlled by arrangement of atoms (like halite cubes). Above are equant crystals of garnet, halite cubes). Above are equant crystals of garnet, with same dimensions in all directions. with same dimensions in all directions. Fig. 2-7a, p.30

Fibrous appearance of asbestos. Fibrous appearance of asbestos.

Fig. 2-7b, p.30

Bladed crystals of kyanite. Bladed crystals of kyanite.

Fig. 2-7c, p.30

Some minerals occur in more than one habit. Quartz Some minerals occur in more than one habit. Quartz grows as elongated crystals (left) and as massive grows as elongated crystals (left) and as massive crystals with no characteristic shape. crystals with no characteristic shape.

Fig. 2-8, p.30

CleavageCleavage

Tendency of some minerals to break along flat surfaces. These Tendency of some minerals to break along flat surfaces. These surfaces are planes of weak bonds in the crystal. Mica (for surfaces are planes of weak bonds in the crystal. Mica (for example; above) has one set of parallel cleavage planes. example; above) has one set of parallel cleavage planes. Minerals can have 1, 2, 3 or even four different sets of cleavage Minerals can have 1, 2, 3 or even four different sets of cleavage planes that can be described as excellent to poor and none. planes that can be described as excellent to poor and none. Fig. 2-9, p.31

A flat surface created by cleavage, and a flat A flat surface created by cleavage, and a flat surface that is a crystal face can appear surface that is a crystal face can appear identical. Cleavage surface is duplicated identical. Cleavage surface is duplicated when a crystal is broken, a crystal face is not. when a crystal is broken, a crystal face is not.

Above: feldspar has two cleavages at right Above: feldspar has two cleavages at right angles; calcite has three sets of cleavage, not angles; calcite has three sets of cleavage, not a right angles (deformed box look); fluorite a right angles (deformed box look); fluorite has four cleavage planes (double pyramid has four cleavage planes (double pyramid look); quartz has no cleavage (right), but look); quartz has no cleavage (right), but fractures. fractures.

Fig. 2-10, p.31

FeldsparFeldspar

Fig. 2-10a, p.31

CalciteCalcite

Fig. 2-10b, p.31

FluoriteFluorite

Fig. 2-10c, p.31

FractureFracture: the manner in which a mineral breaks, not : the manner in which a mineral breaks, not along cleavage planes. Conchoidal fracture, shown along cleavage planes. Conchoidal fracture, shown above (smoky quartz) creates smooth, curved above (smoky quartz) creates smooth, curved surfaces. surfaces. Fig. 2-11, p.32

Table 2-11, p.32

Hardness: resistance of a mineral to scratchingHardness: resistance of a mineral to scratching

Specific GravitySpecific Gravity

Weight of a substance relative to an equal Weight of a substance relative to an equal volume of water. Most common minerals have volume of water. Most common minerals have a specific gravity of 2.7 (the mineral weighs 2.7 a specific gravity of 2.7 (the mineral weighs 2.7 times that of an equal volume of water).times that of an equal volume of water).

Gold’s specific gravity is 19.Gold’s specific gravity is 19.

Use “heft” to determine a mineral’s approximate Use “heft” to determine a mineral’s approximate specific gravity.specific gravity.

ColorColor

Color is the most obvious property of a mineral, Color is the most obvious property of a mineral, but can be the most unreliable for identification. but can be the most unreliable for identification. Chemical impurities and imperfections in the Chemical impurities and imperfections in the crystal structure can dramatically alter the color.crystal structure can dramatically alter the color.

Quartz, for example, can occur in many colors Quartz, for example, can occur in many colors including white, clear, black, purple and red as including white, clear, black, purple and red as a result of tiny amounts of impurities and minor a result of tiny amounts of impurities and minor defects in the ordering of atoms. defects in the ordering of atoms.

StreakStreak Streak is the color of the fine powder of a Streak is the color of the fine powder of a

mineral. Rub the mineral across a porcelain mineral. Rub the mineral across a porcelain plate called a streak plate. Many minerals plate called a streak plate. Many minerals leave a diagnostic color.leave a diagnostic color.

Hematite (iron oxide), for example, can be dull Hematite (iron oxide), for example, can be dull red to shiny black in color, but it always leaves red to shiny black in color, but it always leaves a red powder on a streak plate (so can be more a red powder on a streak plate (so can be more reliable than color for identification).reliable than color for identification).

Luster:Luster:

This is the manner This is the manner in which a mineral in which a mineral reflects light. A reflects light. A mineral with a mineral with a metallic look has a metallic look has a metallic luster. metallic luster. Pyrite (to right) Pyrite (to right) has a metallic has a metallic luster. Non-luster. Non-metallic luster can metallic luster can be described by be described by terms such as terms such as glassy, pearly, glassy, pearly, earthy, resinous earthy, resinous and vitreous. and vitreous.

Fig. 2-12, p.13

Other PropertiesOther Properties

These include reaction to acid (calcite and These include reaction to acid (calcite and other carbonates liberate Co2), magnetism other carbonates liberate Co2), magnetism (magnetite), radioactivity (uranium), (magnetite), radioactivity (uranium), fluorescence (when exposed to utraviolet fluorescence (when exposed to utraviolet light), phosphorescence and double refraction. light), phosphorescence and double refraction.

Mineral Classes and the Rock-Forming Mineral Classes and the Rock-Forming MineralsMinerals

Minerals are classified by their abundant Minerals are classified by their abundant chemical elements (Table 2.3). Of all the chemical elements (Table 2.3). Of all the minerals, nine are the most common rock-minerals, nine are the most common rock-forming minerals in the crust. Seven are forming minerals in the crust. Seven are silicates (containing silicon and oxygen) and the silicates (containing silicon and oxygen) and the other two are carbonates (containing carbon other two are carbonates (containing carbon and oxygen). and oxygen).

Silicates: make up 92% Silicates: make up 92% of the Earth’s crust. of the Earth’s crust. Most abundant because Most abundant because oxygen and silicon are oxygen and silicon are the most abundant the most abundant elements in the Earth’s elements in the Earth’s crust (and they readily crust (and they readily combine). Feldspars are combine). Feldspars are the most common the most common silicates, then pyroxene silicates, then pyroxene and quartz. Silicate and quartz. Silicate tetrahedron commonly tetrahedron commonly link together by sharing link together by sharing oxygen atoms. oxygen atoms.

Fig. 2-13, p.13

Every silicon atom Every silicon atom in the Earth’s in the Earth’s crust surrounds crust surrounds itself with four itself with four oxygen atoms. oxygen atoms. The bonds are The bonds are strong. This strong. This pyramid shaped pyramid shaped structure is called structure is called the silicate the silicate tetrahedron, and tetrahedron, and is the is the fundamental fundamental building block of building block of all silicate all silicate minerals.minerals.

Fig. 2-13a, p.13

Most silicate tetrahedra combine with additional elements Most silicate tetrahedra combine with additional elements (cations such as aluminum, iron, calcium, potassium, sodium (cations such as aluminum, iron, calcium, potassium, sodium and magnesium). Quartz is the only common silicate that and magnesium). Quartz is the only common silicate that contains only Si and O. Silicate tetrahedra commonly link by contains only Si and O. Silicate tetrahedra commonly link by sharing oxygen atoms to form chains, sheets, or other three-sharing oxygen atoms to form chains, sheets, or other three-dimensional networks (Figure 2.14). dimensional networks (Figure 2.14). Fig. 2-13b, p.13

Table 2-3, p.34

Rock-Rock-forming forming silicates fall silicates fall into five into five main main groups, groups, based on based on the way the the way the tetrahedra tetrahedra link link together.together.

Fig. 2-14, p.15

Feldspar alone makes up about half of the Earth’s Feldspar alone makes up about half of the Earth’s crust. Quartz composes 12% of the Earth’s crust, and crust. Quartz composes 12% of the Earth’s crust, and is widespread and abundant in continental rocks. is widespread and abundant in continental rocks.

Fig. 2-16, p.36

OlivineOlivine

Fig. 2-15a, p.36

PyroxenePyroxene

Fig. 2-15b, p.36

AmphiboleAmphibole

Fig. 2-15c, p.36

BiotiteBiotite

Fig. 2-15d, p.36

ClayClay

Fig. 2-15e, p.36

FeldsparFeldspar

Fig. 2-15f, p.36

QuartzQuartz

Fig. 2-15g, p.36

Calcite: CaCO3Calcite: CaCO3

A carbonate A carbonate mineral much mineral much less common less common than silicates in than silicates in the Earth’s crust, the Earth’s crust, but important but important rock-forming rock-forming minerals minerals because found because found in sedimentary in sedimentary rocks across the rocks across the continents. continents.

Fig. 2-15h, p.36

Dolomite: Dolomite: CaMg (C03)2CaMg (C03)2

Another Another carbonate.carbonate.

Shells and Shells and other hard other hard parts of many parts of many marine marine organisms are organisms are made of made of carbonate carbonate minerals, and minerals, and accumulate to accumulate to form limestone.form limestone.

Fig. 2-15i, p.36

Commercially Important MineralsCommercially Important Minerals Many minerals, although not abundant, are Many minerals, although not abundant, are

commercially important. Our society depends on commercially important. Our society depends on metals such as iron, copper, lead, zinc, gold and metals such as iron, copper, lead, zinc, gold and silver.silver.

Ore minerals: minerals from which metals or other Ore minerals: minerals from which metals or other elements can be profitably recovered. Gold and silver elements can be profitably recovered. Gold and silver occur as single elements; iron is bonded to oxygen; occur as single elements; iron is bonded to oxygen; copper, lead and zinc commonly bonded to sulfur.copper, lead and zinc commonly bonded to sulfur.

Industrial Minerals: commercially important, but not Industrial Minerals: commercially important, but not considered an ore (not mined for metals). Examples considered an ore (not mined for metals). Examples are halite mined for table salt; gypsum for ?; limestone are halite mined for table salt; gypsum for ?; limestone for ?; sulfur for?for ?; sulfur for?

Gems: minerals of beauty (diamonds also used Gems: minerals of beauty (diamonds also used industrially). industrially).

Galena is the most important ore of leadGalena is the most important ore of lead

Fig. 2-17, p.37

Native sulfur occurs at vents of dormant and active Native sulfur occurs at vents of dormant and active volcanoes.volcanoes.

Fig. 2-18, p.37

Sapphire is one of the most costly precious gemsSapphire is one of the most costly precious gems

Fig. 2-19, p.38

Topaz is a popular semiprecious gemTopaz is a popular semiprecious gem

Fig. 2-20, p.38

Environmentally Hazardous Rocks and Environmentally Hazardous Rocks and MineralsMinerals

Usually in their natural states, most rocks and Usually in their natural states, most rocks and minerals are environmentally benign and minerals are environmentally benign and harmless to humans (or we wouldn’t survive). harmless to humans (or we wouldn’t survive). A few are harmful and dangerous (asbestos for A few are harmful and dangerous (asbestos for example is cancer-causing). example is cancer-causing).

Most hazardous rocks and minerals are buried Most hazardous rocks and minerals are buried and through natural processes are exposed so and through natural processes are exposed so slowly that they release toxic materials in low slowly that they release toxic materials in low concentrations. Irresponsible mining can concentrations. Irresponsible mining can concentrate and release hazardous materials. concentrate and release hazardous materials.

One form of asbestos occurs as long, curly fibers.One form of asbestos occurs as long, curly fibers.

Fig. 2-21a, p.39

One form of asbestos occurs as short, sharply pointed One form of asbestos occurs as short, sharply pointed needles.needles.

Fig. 2-21b, p.39

Acid mine drainage can poison aquatic life and stain Acid mine drainage can poison aquatic life and stain stream beds and banks. stream beds and banks. Fig. 2-22, p.41

p.42