What is a Mineral Its more than just

What is a Mineral? It’s more than just a pretty stone! 9/24/2020 1

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11. 1 How Do Geological Processes Relate to Society and the Environment? § Mineral resources are produced by geological processes active at the surface and within Earth. § Earth’s rock cycle takes millions of years to produce mineral resources, making minerals a nonrenewable resource.

What Are Minerals? § Naturally occurring, chemical elements or inorganic compounds (solids) with regularly arranged atoms or ions § Mineral resource: one or more minerals that can be extracted, processed, and used in manufacturing § Some contain only one element (gold, lanthanum, salt), others contain more than one element as in an inorganic compound (quartz and rare earth oxides)

CONCEPT REVIEW § EARTH IS MOSTLY MADE UP OF ROCK § ROCKS ARE MADE UP OF MINERALS § THERE ARE 3800+ NAMED MINERALS § MOST ROCKS ARE MADE OF JUST A FEW OF THESE

What Are Rocks? § Rocks: solid collections of one or more minerals in Earth’s crust § Sedimentary rocks (sandstones, shale) § Sediments compacted and cemented into rock § Igneous rocks (granite, lava rock) § Cooled magma and lava § Metamorphic rocks (slate, marble) § Exposed and altered by high pressures and temperatures

Recycling of Earth’s Rocks § Rock cycle: the interaction of physical and chemical processes that work to change rocks from one kind to another § Recycling processes: erosion, melting, metamorphism § The rock cycle can take millions of years, so these resources are considered nonrenewable.

The Rock Cycle

Characteristics of Minerals § In order to be classified as a mineral, a substance MUST: § Be naturally occurring § Be inorganic (generally) § Be a solid § Have a definite chemical composition § Have a repeating crystal lattice 9/24/2020 9

Naturally Occurring § Mineral must be found in nature § Not artificially created in the lab § For example – cubic zirconium is NOT a mineral since it is artificial only § However, halite created in the lab IS a mineral because it is also found in nature 9/24/2020 10

Generally Inorganic § Inorganic substances are non-living (past, present, future) § Mineral can not be formed from living things § Exception – calcite is produced by living sea creatures 9/24/2020 11

Generally Inorganic § Inorganic substances are NOT carbon-based § However, a mineral CAN contain carbon (calcite – Ca. CO 3) § Other exceptions are Graphite (C) and Diamond (C) 9/24/2020 12

Solid § Minerals cannot be liquids or gases § For example – water is NOT a mineral, but glacial ice IS a mineral 9/24/2020 13

Repeating Crystal Lattice § A lattice is a repeating structural pattern § For example – quartz ALWAYS has one silicon atom bonded to four oxygen atoms § Chemistry note – strong bonds are why minerals are solids! 9/24/2020 14

Definite Chemical Formula (Composition) § A mineral must have a definite chemical composition that identifies it as unique. § For example – halite is Na. Cl § Some minerals do have minor variations in their formulas §For example – Feldspar can be made from potassium, calcium, or magnesium 9/24/2020 15

Definite Chemical Formula § Minerals are expressed by a specific chemical formula -Gold (Au) -Calcite (Ca. CO 3) -Quartz (Si. O 2) -Pyrite (Fe. S 2) -Halite (Na. Cl)

Definite Chemical Composition 9/24/2020 17

Repeating Crystal Lattice § Minerals with the same chemical composition can have different lattices – making them different minerals! § For example – take a look at these lattices for Diamond (C) and Graphite (C). 9/24/2020 18

How are minerals formed? § Minerals are formed by five basic processes § Cooling of magma § Precipitation (not rain!) § Metamorphism § Chemical Weathering § Hydrothermal Solutions § Type of mineral formed is based on process 9/24/2020 19

Cooling of Magma § Magma is a molten “soup” of minerals § As it cools, certain minerals crystallize at different temperatures § This removes some elements from the magma and changes its composition 9/24/2020 20

Precipitation § Precipitation here refers to the formation of a solid from a liquid § Can be as simple as evaporation or a chemical reaction where two liquids combine to form a solid § Calcite, gypsum, and halite form this way. 9/24/2020 21

Metamorphism § Metamorphism is a change in a mineral (or rock) brought about by changes in heat and pressure. § Increased heat and/or pressure causes mineral structure (lattices) to change – resulting in a new mineral § Minerals can be recrystallized or foliated (aligned in layers) § Examples include talc, kyanite, garnet, and sillimanite 9/24/2020 22

Metamorphism 9/24/2020 23

Chemical Weathering § Chemical weathering of minerals occurs at the surface of the earth in soils and clays § Chemical reactions take place and change the mineral structures – resulting in a new mineral § For example – orthoclase reacts with acid rain to form kaolinite 9/24/2020 24

Hydrothermal Solutions § A hydrothermal solution is a hot water solution containing a variety of substances § The temperature of the water allows a great deal of mixing and reacting to take place § Results in numerous combinations of substances – forming many minerals § Sulfides are often formed this way 9/24/2020 25

Summary § A mineral is a naturally occurring solid with a definite chemical formula and crystal lattice and is generally inorganic. § Minerals can form in five common ways – magma cooling, precipitation, metamorphism, chemical weathering, and hydrothermal solutions. 9/24/2020 26