Inside the Restless Earth Ch. 1 Minerals of the Earth’s Crust

Section 1: What Is a Mineral?

Section 1: What is a Mineral? Naturally formed Inorganic Solid Crystalline structure

Mineral Structure element - a substance that cannot be separated or broken down into simpler substances by chemical means. Each element is made of only one kind of atom. The element sodium.

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Mineral Structure compound - a substance made of two or more elements that have been chemically combined. Na + Cl = NaCl The compound halite.

Mineral Structure crystal - a solid whose atoms, ions, or molecules are arranged in a definite repeating pattern. The arrangement of atoms is determined by the kinds of atoms. Amethyst.

Two Groups of Minerals Minerals are divided into two groups based on their chemical composition.

Two Groups of Minerals 1. Silicate minerals - minerals that contain a combination of silicon, oxygen, and often one or more metals. - Make up > 90% of Earth’s crust

Common Silicate Minerals Feldspar KAlSi3O8 Quartz Silicon Dioxide SiO2 Mica Biotite K(Mg, Fe)3AlSi3O10(F, OH)2

Two Groups of Minerals 2. Nonsilicate minerals - minerals that do not contain compounds of silicon and oxygen. Gypsum

Classes of Nonsilicate Minerals Native Elements - composed of only one element. Gold Copper

Classes of Nonsilicate Minerals Oxides - form when an element (such as aluminum or iron) combines chemically w/ oxygen. Corundum Al2O3 Aluminum oxide

Classes of Nonsilicate Minerals Carbonates - contain combinations of carbon and oxygen in their chemical structure. Calcite CaCO3

Classes of Nonsilicate Minerals Sulfates - contain sulfur and oxygen, SO4. Gypsum Calcium Sulfate Dihydrate CaSO4·2H2O

Classes of Nonsilicate Minerals Halides - form when: flourine, chlorine, iodine, or bromine combine with sodium, potassium, or calcium Flourite Calcium Fluoride CaF2

Classes of Nonsilicate Minerals Sulfides - contain one or more elements (such as lead, iron, or nickel) combined with sulfur. Galena Lead Sulfide PbS

Section 2: Identifying Minerals

Section 2: Identifying Minerals Color - the same mineral can come in a variety of colors - usually not the best way to identify a mineral

Section 2: Identifying Minerals Luster - the way a surface reflects light.

Section 2: Identifying Minerals Luster - the way a surface reflects light. 1. Metallic - bright, reflective Gold

Section 2: Identifying Minerals 2. Submetallic - dull, reflective Euxenite

Section 2: Identifying Minerals 3. Nonmetallic Vitreous glassy, brilliant Pollucite

Section 2: Identifying Minerals 3. Nonmetallic Silky fibrous Gypsum

Section 2: Identifying Minerals 3. Nonmetallic Resinous plastic Sphalerite

Section 2: Identifying Minerals 3. Nonmetallic Waxy greasy, oily Cancrinite

Section 2: Identifying Minerals 3. Nonmetallic Pearly creamy Stellerite

Section 2: Identifying Minerals 3. Nonmetallic Earthy rough, dull Kaolinite

Section 2: Identifying Minerals Streak - the color of a mineral in powdered form. - the mineral is rubbed against a streak plate - streak is not affected by air or water - more reliable than mineral color

Cleavage and Fracture Cleavage - the tendency of some minerals to break along smooth, flat surfaces.

Cleavage and Fracture Fracture - the tendency of some minerals to break unevenly along curved or irregular surfaces. Conchoidal fracture

Hardness Hardness - a mineral’s resistance to being scratched.

Density Density - measure of how much matter is in a given amount of space. d = m / v gold = 19 g/cm3 Specific gravity - the ratio of an object’s density to the density of water. gold = 19

Special Properties Fluorescence - glow under ultraviolet light. Calcite (red) and willemite (green)

Special Properties Chemical reaction - look for bubbling when combined with an acid. CaCO3 + 2HCl = CO2 + H2O + CaCl2 calcite hydrochloric acid

Special Properties Optical properties - such as double refraction. Same sample of calcite, but it’s rotated.

Special Properties Magnetism - attracts iron. Magnetite

Special Properties Taste Never taste a mineral without the teacher’s permission. Halite tastes salty. Borax tastes sweet.

Special Properties Radioactivity Autunite contains uranium.

Section 3: The Formation, Mining, and Use of Minerals

How Do Minerals Form? Limestones As water runs along the surface of the Earth and seeps through the ground, it dissolves minerals and carries them to large bodies of water, where they crystallize on the bottom.

How Do Minerals Form? Evaporating Salt Water Minerals such as halite crystallize when salt water evaporates.

How Do Minerals Form? Metamorphic Rocks Changes in pressure, temperature, or chemical makeup can form new minerals such as garnet.

How Do Minerals Form? Hot-Water Solutions Magma heats groundwater, which now more easily reacts with and dissolves minerals. The minerals then crystallize out of the solution. This vein of gold was formed this way.

How Do Minerals Form? Pegmatites Magma can move upward into these teardrop-shaped bodies. Pictured here is a sample of tourmaline from a pegmatite.

How Do Minerals Form? Plutons As magma moves up it may cool and solidify forming a pluton.

Mining Ore: A mineral deposit large enough and pure enough to be mined for profit.

Mining Surface Mining Used to remove minerals located at or near the surface of the Earth.

Mining Subsurface Mining Used to remove minerals located too deep within the Earth to be surface mined.

Responsible Mining Potential mining problems: - Can disturb or destroy habitats - Waste products may pollute surface water and groundwater

Responsible Mining Potential mining problems: Solutions: - Can disturb or destroy habitats - Waste products may pollute surface water and groundwater Solutions: - Reclamation: return mined land to its original state - Reduce need for minerals by recycling

The Use of Minerals Metallic Minerals - Have shiny surfaces - Do not let light pass through them - Good conductors of heat and electricity

The Use of Minerals Nonmetallic Minerals - Have shiny or dull surfaces - May let light pass through them - Good insulators of electricity

The Use of Minerals Gemstones - Highly valued for beauty and rarity