Chapter 1 Minerals: Building Blocks of Rocks

Minerals: Building Blocks of Rocks By definition a mineral is/has Naturally occurring Inorganic solid Ordered internal molecular structure Definite chemical composition

Rocks are an aggregate of minerals

Composition and Structure of Minerals Atoms Elements MineralsRocks

Earth Composition Earth Consists of the Core, Mantle, and Crust

Elemental Abundances in Continental Crust Figure 1.14

Elemental Abundances Earth as a whole vs Crust Oxygen35% Iron24% Silicon17% Magnesium 14% Sulfur6% Aluminum1% Calcium 1% Earth Oxygen47% Iron5.5% Silicon27% Magnesium 2.1% Sulfur<1% Aluminum8% Calcium 3.7% Crust

Composition and Structure of Minerals Elements Basic building blocks of minerals Over 100 are known (92 naturally occurring) Atoms Smallest particles of matter Retain all the characteristics of an element

Composition and Structure of Minerals Atomic structure Central region called the nucleus Consists of protons (+ charges) and neutrons (- charges) Electrons Negatively charged particles that surround the nucleus Located in discrete energy levels called shells

Structure of an Atom Figure 1.5 A

Structure of an Atom Figure 1.5 A

Composition and Structure of Minerals Chemical bonding Formation of a compound by combining two or more elements Atoms gain or lose outermost electrons to form ions Oppositely charged ions attract one another to produce a neutral chemical compound

Composition and Structure of Minerals Isotopes and radioactive decay Mass number = sum of neutrons + protons in an atom Isotope = atom that exhibits variation in its mass number Unstable isotopes emit particles and energy in a process known as radioactive decay

Physical Properties of Minerals Crystal form External expression of a mineral’s internal structure Often interrupted due to competition for space and rapid loss of heat

A Garnet Crystal

Cubic Crystals of Pyrite Figure 1.7 A

Physical Properties of Minerals Luster Appearance of a mineral in reflected light Two basic categories Metallic Nonmetallic Other descriptive terms include vitreous, silky, or earthy

Galena (PbS) Displays Metallic Luster Figure 1.13

Physical Properties of Minerals Color Generally unreliable for mineral identification Often highly variable due to slight changes in mineral chemistry Exotic colorations of certain minerals produce gemstones

Quartz (SiO 2 ) Exhibits a Variety of Colors

Physical Properties of Minerals Streak Color of a mineral in its powdered form Hardness Resistance of a mineral to abrasion or scratching All minerals are compared to a standard scale called the Mohs scale of hardness

Streak Is Obtained on an Unglazed Porcelain Plate Figure 1.8

Mohs Scale of Hardness Figure 1.9

Physical Properties of Minerals Cleavage Tendency to break along planes of weak bonding Produces flat, shiny surfaces Described by resulting geometric shapes Number of planes Angles between adjacent planes

Fluorite, Halite, and Calcite All Exhibit Perfect Cleavage Figure 1.11

Physical Properties of Minerals Fracture Absence of cleavage when a mineral is broken Specific Gravity Weight of a mineral/weight of an equal volume of water Average value = 2.5 – 3.0

Conchoidal Fracture Figure 1.12

Physical Properties of Minerals Other properties Magnetism Reaction to hydrochloric acid Malleability Double refraction Taste Smell Elasticity

Mineral??????? QuartzYesNo CoalYesNo PearlsYesNo AmethystYesNo ShellsYesNo WaterYesNo IceYesNo Iron YesNo

Mineral Groups Nearly 4000 minerals have been named Rock-forming minerals Common minerals that make up most of the rocks of Earth’s crust Only a few dozen members Composed mainly of the 8 elements that make up over 98% of the continental crust

Mineral Groups Silicates Most important mineral group Comprise most rock-forming minerals Very abundant due to large % of silicon and oxygen in Earth’s crust Silicon-oxygen tetrahedron Fundamental building block Four oxygen ions surrounding a much smaller silicon ion

Two Illustrations of the Si–O Tetrahedron Figure 1.15

Mineral Groups Common silicate minerals Feldspar group Most common mineral group Quartz Only common silicate composed entirely of oxygen and silicon

Potassium Feldspar Figure 1.17

Mineral Groups Important nonsilicate minerals Comprise only 8% of Earth’s crust Often occur as constituents in sedimentary rocks

Table 1.1

Mineral Groups Important nonsilicate minerals Carbonates Primary constituents in limestone and marble Limestone is used commercially for road paving, building stone, and as the main ingredient in Portland cement

Mineral Groups Important nonsilicate minerals Halite and gypsum Both are commonly found in thick layers Like limestone, both halite and gypsum are important nonmetallic resources

Mineral Groups Important nonsilicate minerals A number of other minerals have economic value Examples Hematite (oxide mined for iron ore) Sphalerite (sulfide mined for zinc ore) Galena (lead) Native copper (native element mined for copper)

Native Copper

Mineral Resources and Reserves Resources are minerals that can be recovered for use Reserves include mineral deposits already identified that can be profitability extracted Resources include reserves, deposits that can not economically recovered, and minerals not yet discovered

Florida Production 4 th in states for non fuel minerals Top 3 in the states for crushed stone, cement, and peat 1 st in states in heavy mineral sales 1 st in world for phosphate production

Florida Production - Phosphate 90% used for fertilizer 5% for livestock feed supplement 5% used in food products, chemicals and ceramics

Florida Production – Crushed Stone Limestone and coquina Used for construction Limestone used for cement

Florida Production – Clays Used for absorbents, anti-acids, and whiteners

Florida Production – Heavy Minerals Found in Sands Main minerals include ilmenite and rutile – both metamorphic minerals Used as paint pigments, paper, and plastics

End of Chapter 1