Minerals will be covered in some detail in Chapter 2, but here we will briefly touch on what minerals are, and how they are related to rocks. A mineral is a naturally occurring combination of specific elements that are arranged in a particular repeating three-dimensional structure or lattice. Even in a tiny crystal, like the ones in your salt shaker, the lattices extend in all three directions for thousands of repetitions.
Halite always has this composition and this structure. There are thousands of minerals, although only a few dozen are mentioned in this book. In nature, minerals are found in rocks, and the vast majority of rocks are composed of at least a few different minerals. A close-up view of granite, a common rock, is shown in Figure 1. Although a hand-sized piece of granite may have thousands of individual mineral crystals in it, there are typically only a few different minerals, as shown here.
Rocks can form in a variety of ways. Igneous rocks are classified into two groups depending upon where the molten rock solidifies: Extrusive or Intrusive. Felsic : Derived from the words feldspar and silica to describe an igneous rock having abundant light-colored minerals such as quartz, feldspars, or muscovite.
Mafic : Derived from the words magnesium and ferric Fe is the chemical symbol for iron to describe an igneous rock having abundant dark-colored, magnesium- or iron-rich minerals such as biotite, pyroxene, or olivine. Extrusive, or volcanic, igneous rock is produced when magma exits and cools as lava at or near the Earth's surface. Exposed to the relatively cool temperatures of the atmosphere, the lava cools quickly meaning that mineral crystals don't have much time to grow. This results in rocks with a very fine-grained or even glassy texture.
Hot gasses are often trapped in the quenched lava, forming bubbles vesicles. Types of extrusive igneous rocks include: pumice, obsidian, andesite, rhyolite, and basalt. Volcanic processes has shaped the extrusive igneous rock formations at these parks:. Intrusive, or plutonic, igneous rock forms when magma remains inside the Earth's crust where it cools and solidifies in chambers within pre-existing rock.
The magma cools very slowly over many thousands or millions of years until is solidifies. Slow cooling means the individual mineral grains have a very long time to grow, forming a rock with large, visible crystals. In the language of economic geology, Earth materials are classified as metallic ores, fuel minerals, gemstones, and industrial minerals.
Most people know that metallic ores yield shiny, conductive, ductile elements such as copper, iron, or gold. Most understand that energy-producing coals constitute a fuel mineral. Likewise, dazzling rubies and This teacher's guide defines what a mineral deposit is and how a mineral deposit is identified and measured, how the mineral resources are extracted, and how the mining site is reclaimed; how minerals and mineral resources are processed; and how we use mineral resources in our every day lives.
Included are 10 activitybased learning exercises that Minerals and mineral resources are a part of our everyday lives. This poster depicts a home and shows the different mineral s and mineral materials used to make the various products found in the average home. Minerals are found everywhere in our daily lives.
Designed for K-8 Teachers this poster can be scaled and is printable at 36" x 60" and legible at 11" x 17" in size. It also describes the ideal mineral deposit.
In , these five states led the pack in mineral production, accounting for about one third of the total mineral production value for the entire country. Ever wondered what the difference between a rock and a mineral was? This EarthWord should cover it The naturally occurring material from which a mineral or minerals of economic value can be extracted.
Usually minerals, especially metals, are mined first in ore form, then refined later. Mineral : Feldspar Primary Commodity : Feldspar Primary Commodity Uses : Feldspar is one of the most common minerals on the planet and is mostly used for glassmaking and ceramics. Mineral : Rutile Primary Commodity : Titanium Primary Commodity Uses : The vast majority of titanium is used in whiteners in the form of titanium oxide.
Titanium metal makes up a comparatively small amount of the use for titanium, but as a metal it is used in metal coatings and medical implants. A sample of pyrite and quartz.
Iron pyrite, also known as Fool's Gold due to its resemblance to gold, often occurs in quartz veins. Pyrite is an important source of sulfur dioxide, which is primarily used to create sulfuric acid, an important industrial acid. In fact, consumption of sulfuric acid has been regarded as one of the best indexes of a nation's industrial.
Sample originated from Prince of Wales Island, Alaska, and is 6. A sample of augelite and quartz. Augelite is an aluminum phosphate mineral, primarily prized for collecting rather than as a source for its industrial mineral components. Sample originated from Mundo Nuevo Mine, Peru, and is 3. Diopside crystals are made up of Magnesium, Calcium, Silicon and Oxygen, and are usually found in metamorphic rocks. These crystals have developed in some Cockeysville Marble from Texas, Maryland.
An image of calcite. Credit: Rob Lavinsky, iRocks. In Arkansas, the overwhelming majority of surface and near-surface rocks are sedimentary rocks. There are a few igneous rocks and some very low-grade metamorphic rocks, but these occupy little area.
In the Ozark Plateau and Ouachita Mountains , there are indications of some very low-grade metamorphic effects on the rocks in restricted areas, but because their degree of alteration is slight, geologists still treat them as sedimentary rocks.
A few true metamorphic rocks are found due to the alteration of the rocks immediately surrounding and in contact with the igneous intrusions. All rocks are composed of mineral grains. A mineral is a chemical compound that has certain specific characteristics: it is naturally occurring, inorganic, and has a definite chemical composition and molecular structure within limits. Over different minerals are found in Arkansas, either as discrete deposits or as the mineral grains making up the rocks themselves.
Only a handful of these minerals are common. The bedrock of the Ozark Plateau portion of Arkansas is made up of sedimentary rocks. Most of these rocks fall into just six major types: limestones, dolostones, cherts, sandstones, siltstones, and shales. A few conglomerates, breccias, and other types may occur in limited places. Few rock layers are pure, so many mixtures and combinations of these types will be found, such as shaly limestones or dolomitic sandstones.
The sediments that make up these rocks were deposited in an ocean basin on a continental shelf. These sedimentary rocks were laid down in that marine environment from to million years ago during the Paleozoic era.
The limestones are composed primarily of the mineral calcite CaCO 3 , derived predominantly from the shells and skeletons of the various animals and plants that lived in those ancient oceans. Dolostones are quite similar to limestones and are generally found in older rock layers middle Ordovician period, about million years ago, and earlier.
Dolomite CaMg CO 3 2 is the principal mineral of a dolostone. It is thought that most of the dolostone was once limestone that has been altered over time. Chert is a cryptocrystalline silica SiO 2 usually occurring as nodules or thin beds in certain intervals of limestone or dolostone. However, in a few places, chert has replaced the original bedrock and may make up a notable portion of the rock sequence.
Sandstones and siltstones are very similar rock types, just differing in grain sizes that, in turn, reflect the different energy environments of the depositional setting. Almost all of the sand and silt making up these rocks are fragments of quartz SiO 2. The shales are very fine-grained rocks composed mostly of clay and silt mud. Shale is finely stratified and readily splits into thin layers. All of these rocks are composed of sediment grains cemented together. The most common cements are calcite, dolomite, quartz, clay, and iron oxide.
As the hot water solutions cooled, they deposited the various minerals dissolved in them. In places scattered across the region, small deposits of galena PbS and sphalerite ZnS , along with quartz and traces of pyrite FeS 2 and chalcopyrite CuFeS 2 , are present. As these hot solutions moved through the host rock, they dissolved some of the minerals making up the rock only to re-deposit them later upon cooling, leaving crystalline calcite and dolomite.
Weathering and erosion have added some rock and mineral deposits to the region as well. Manganese and iron minerals concentrated by these processes occur in a few places.
Groundwater has also left its mark by dissolving the limestones and similar rocks and then redepositing the dissolved calcite as crystalline calcite or aragonite chemically the same as calcite but with a different molecular structure as travertine, the rock of cave formations.
The Arkansas River Valley is underlain by sandstones, siltstones, and shales of Pennsylvanian age — million years ago.
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