Chapter 2 Minerals

2.2 Minerals Definition of a Mineral 1. D-Definite chemical composition 2. I-Inorganic (not containing both carbon & hydrogen) 3. N-Naturally occurring 4. C-Crystalline structure (atoms are arranged orderly & repetitively) 5. S-Solid substance Crystals

2.2 How do Minerals Form? Minerals form nearly everywhere on Earth under different conditions There are FOUR major processes by which minerals form Crystallization from magma Precipitation Changes in pressure & temperature Hydrothermal solutions

2.2 Crystallization Crystallization - Minerals in molten rock crystallize as the rock cools muscovite feldspar quartz hornblende

Precipitation 2. Precipitation—dissolved substances in water can form minerals as the water evaporates limestone halite

2.2 Pressure & Temperature 3. Pressure and temperature —existing minerals can create new minerals by rearranging the crystalline structure Ex: talc

2.2 Hydrothermal Solutions 4. Hydrothermal solutions—mixture of hot water and dissolved substances form new minerals through chemical reactions when they mix with existing minerals or when the mixture cools

2.2 Minerals Mineral Groups  Can be classified based on their composition 1. Silicates Silicon and oxygen combine to form a structure called the silicon-oxygen tetrahedron. This silicon-oxygen tetrahedron provides the framework of every silicate mineral. Most abundant mineral group—75% crust

The Silicon-Oxygen Tetrahedron 1 Silicon atom 4 Oxygen atoms

Silicon-Oxygen Chains, Sheets, and Three-Dimensional Networks

2.2 Minerals Mineral Groups 2. Carbonates 3. Oxides Minerals that contain the elements carbon, oxygen, and one or more other metallic elements Ex: Limestone, marble 3. Oxides Minerals that contain oxygen and one or more other elements, which are usually metals

Carbonates Calcite Dolomite

Oxides Corundum Hematite

2.2 Minerals Mineral Groups 4. Sulfates and Sulfides 5. Halides Minerals that contain the element sulfur Ex: pyrite (fool’s gold) 5. Halides Minerals that contain a halogen ion plus one or more other elements Ex: Salt (halite) 6. Native elements Minerals that exist in relatively pure form Ex: Gold, Silver, Copper, Sulfur, Diamond, Graphite

Sulfides Galena Pyrite

Halides Fluorite Halite

Native Elements Copper Gold

2.3 Properties of Minerals Minerals are classified by their physical properties Color Small amounts of different elements can give the same mineral different colors. Different minerals can have the same color Least reliable property

QUARTZ

Corundum Vanadinita Realgar Cinnabar Beryl Red corundum is a ruby. Blue corundum is a sapphire. Green Beryl is an emerald

2.3 Properties of Minerals Streak  Streak is the color of a mineral in its powdered form.

2.3 Properties of Minerals Luster 2.3 Properties of Minerals Luster is used to describe how light is reflected from the surface of a mineral. Metallic Nonmetallic

2.3 Properties of Minerals Crystal Form 2.3 Properties of Minerals Crystal form is the shape the crystals tend to take as they grow (structure) If it forms slowly, it will have well-formed faces (sides, top, bottom) If it forms fast, minerals compete for space Crystal Growth

Quartz Often Exhibits Good Crystal Form.

2.3 Properties of Minerals Hardness 2.3 Properties of Minerals  Hardness is a measure of the resistance of a mineral to scratching and abrasion.  Mohs scale consists of minerals arranged from 10 (hardest) to 1 (softest).

Mohs Scale of Hardness

2.3 Properties of Minerals Cleavage 2.3 Properties of Minerals  Cleavage is the tendency of a mineral to cleave, or break, along flat, even surfaces.

Mica Has Cleavage in One Direction

2.3 Properties of Minerals Fracture 2.3 Properties of Minerals  Minerals that do not show cleavage when broken are said to fracture.  Fracture—the uneven breakage of a mineral

Conchoidal Fracture

Splinter or Fiber Fracture Asbestos

2.3 Properties of Minerals Density 2.3 Properties of Minerals Density (Specific Gravity) is a property of all matter that is the ratio of an object’s mass to its volume. Density = mass (m) volume (V) Density of a pure mineral is a constant value Density can be used to determine the purity or identity of some minerals

2.3 Properties of Minerals Distinctive Properties of Minerals Some minerals can be recognized by other distinctive properties. Magnetism Effervescence—”bubbles” Fluorescence—glow under some conditions Taste—salty, sweet, etc. Touch—greasy, soapy, etc. Smell—rotten eggs, etc.

2.3 Fluorescent Minerals Scheelite Calcite with Zincite and Willemite Inclusions Hardystonite with Willemite, Franklinite, and Calcite Scheelite

2.3 Mineral Resources Where do minerals come from? Resource—the total amount of a mineral material in the Earth Renewable—a mineral resource that is made faster than it is used Non-renewable—a mineral resource that is used faster than it gets made

2.3 Mineral Resources Where do minerals come from? Reserve—the portion of the mineral substance that has been identified Ore—a mineral resource that can be mined profitably

2.3 Mineral Uses Agriculture - fertilizers (superphosphate, limestone, dolomite) Automotive industries - steel, high temperature ceramics (spark plugs, cylinder heads), sulphur (used in vulcanising of rubber), lead and antimony (batteries) etc. Building materials - cement (from calcite), bricks (from clay and shale), glass (from quartz sand), plaster (from gypsum) Chemical industries - manufacture of paints, paper, ceramics, glass Cooking (salt, baking powder) Currency - coins (copper, bronze, nickel, silver, gold) Electronics, copper electrical wiring, computers, space industry - gold, silver, copper, silicon, uncommon metals (gallium, tantalum, tungsten), special glasses and ceramics Jewelry and decorative items (gemstones, gold, silver, platinum) Metallurgy and metal smelting - iron, steel, copper, bronze, brass, lead, zinc, gold, silver, aluminium, special metal alloys etc. Plumbing - copper, lead (in the past) Surgery, medicines, pharmaceuticals, cosmetics (titanium, tantalum and stainless steel implants), dietary supplements (zinc and iron tablets), talcum powder (from talc)