FAQ's about Minerals

What's the difference between a rock and a mineral?
	A rock is an aggregate of one or more minerals; or a body of undifferentiated mineral matter. [ Additional Details and Related Links ]	Click image for additional information.
What is "Fool's Gold?"
	Fool's Gold can be one of three minerals; the most common mineral mistaken for gold is pyrite, chalcopyrite may also appear gold-like, and weathered biotite mica can mimic flake gold. [ Additional Details and Related Links ]	Click image for additional information.
How much gold has been found in the world?
	Of the 193,000 metric tons of gold discovered to date, 62% is found in just four countries on earth. All the gold discovered thus far would fit in a cube 22 meters on a side. [ Additional Details and Related Links ]	Click image for additional information.
What elements are required by animals and plants for survival?
	Understanding our fragile environment often begins with recognition of the importance of certain elements, such as zinc and iron, in relation to animals and plants. This recognition is well deserved because these essential elements are necessary for the life or health of an organism. Some elements such as carbon, hydrogen, oxygen, magnesium, potassium, and phosphorus are required in relatively large amounts by organisms. However, others are required in smaller quantities; these are referred to as trace elements. At the same time, if these or other elements occur in quantities great enough, toxicity can result. An element, or any substance, that occurs in the environment and contains concentrations above what are considered to be safe may be considered a contaminant. When contaminants occur at levels that are potentially harmful to organisms, they are labeled as hazards. Often the quantitative difference between essential amounts and toxic concentrations of these elements is very small. For example, the trace element selenium is required at a level of no less than 0.4 parts per million in the diet of cattle but can be toxic at levels greater than approximately 4 parts per million. There are 15 essential elements to all animals and plants, these include: Hydrogen(H) Carbon (C) Nitrogen (N) Oxygen (O) Sodium (Na) Magnesium(Mg) Phosphorus(P) Sulfur(S) Chlorine (C) Potassium (K) Calcium (Ca) Manganese (Mn) Iron (Fe) Copper (Cu) Zinc (Zn), and Selenium (Se) [ Additional Details and Related Links ]	Click image for additional information.
What are some positive outcomes from volcanoes?
	Over the long term and geologic time, volcanic eruptions and related processes have directly and indirectly benefited mankind. Volcanic materials ultimately break down and weather to form some of the most fertile soils on Earth, cultivation of which has produced abundant food and fostered civilizations. People use volcanic products, the internal heat associated with young volcanic systems has been harnessed to produce geothermal energy, and most of the metallic minerals mined in the world, such as copper, gold, silver, lead, and zinc, are associated with magmas found deep within the roots of extinct volcanoes. -- From: Kious and Tilling, 1996, This Dynamic Earth: The Story of Plate Tectonics: USGS General Interest Publication, and Tilling, 1985, Volcanoes: USGS General Interest Publication. To view maps of volcanoes visit the USGS online store at http://store.usgs.gov/ and look under the heading Maps>Hazards. [ Additional Details and Related Links ]	Click image for additional information.
How can I find field record materials (original field notes and related material made by USGS geologists) and mapping notes?
	The USGS Field Records Library in Denver, Colorado, has an extensive collection of materials. Many of the field records are online at http://www.cr.usgs.gov/. You may contact them at: USGS Field Records Library Box 25046, MS 914 Denver Federal Center Denver, CO 80225-0046 Telephone: 303-236-1000 FAX: 303-236-0015 TDD: 303-236-0998 E-mail: den_lib@usgs.gov To find field record materials related to Alaska, contact: Jill Schneider USGS Mineral Resources Surveys Alaska Section 4200 University Drive Anchorage, AK 99508-4667 Telephone: 907-786-7457 (Office) and 907-786-7007 (Library) FAX: 907-786-7401 E-mail: jschnidr@usgs.gov Two other sources of field records are: 1. National Archives and Records Administration (NARA) in College Park, Maryland, which keeps field record materials in their Archives II facility. Refer to the Guide to Federal Records in the National Archives of the United States (Washington, D.C.: NARA, 1995). Inventory of the Records of the United States Geological Survey, Record Group 57, in the National Archives, part of USGS Circular 1179 (2000, CD-ROM): Records and History of the United States Geological Survey, contains information on USGS and related records accessioned by NARA through 1997 and held at NARA-II. Appendices in this inventory list field records held at NARA-II and by the USGS Field Records Library at Denver. National Archives and Records Administration 8601 Adelphi Road College Park, MD 20740-6001 Telephone: 301-713-6800 (General Reference Information) Telephone: 1-866-272-6272 (Toll Free) E-mail: inquire@nara.gov URL: http://www.archives.gov/index.html 2. Smithsonian Institution Archives includes papers of individuals with close ties to both the USGS and the Smithsonian. Other materials related with the activities of the Smithsonian Institution and the USGS are available there as well. Refer to the Guide to the Smithsonian Archives (Washington, D.C.: Smithsonian Institution Press, 1996) or contact them at the following address: The Smithsonian Institution Archives Arts and Industries Building, Room 2135 900 Jefferson Drive, S.W. Washington, D.C. 20560 Telephone: 202-357-1420 E-mail: OSIAREF@OSIA.SI.EDU The notes made by USGS map surveyors are available in two locations. For topographic mapping notes pertaining to areas of Texas, New Mexico, Colorado, Wyoming, Montana, and states west, including Alaska, contact: Rocky Mountain Mapping Center USGS National Mapping Division Box 25046, MS 506, Federal Center Denver, CO 80225-0046 Telephone: 303-202-4394 For topographic mapping notes pertaining to other geographic areas in the United States, contact: Mid-Continent Mapping Center USGS National Mapping Division MS 309 1400 Independence Road Rolla, MO 65401 Telephone: 573-308-3663 [ Additional Details and Related Links ]	Click image for additional information.
What is a mineral?
	A naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties. [ Additional Details and Related Links ]	Click image for additional information.
How do we get minerals?
	Minerals must be mined from the ground, either by surface, underground, or drilling methods. Sand and gravel is usually mined in surface pits or rock is crushed to size, gold is mined in surface pits, underground mines, and in streams and rivers. [ Additional Details and Related Links ]	Click image for additional information.
What is a thunderegg?
	Oregon's State rock, the "thunderegg," may be the best known gem material from Oregon. Thundereggs were not, as believed by some people, ejected from volcanoes, but formed in very soft and friable volcanic ash beds. Solutions containing silica permeated the cinders until favorable points for chalcedony deposition were achieved. Aggregations of chalcedony were deposited, but before the material could fully solidify the center of the concretion split apart, possibly because of shrinkage, permitting the later introduction of additional materials. The resulting star-shaped centers of chalcedony may be in the form of agate, jasper, or in some cases different varieties of opal. Thundereggs are used in a number of ways. One of the most common uses is to simply saw the thunderegg into two pieces, polish the sawed face of each half, and use it as a display or decorative piece; bookends are also made in this fashion. Also, the thundereggs are sawed into slabs from which calibrated and freeform cabochons are cut. Additionally, at least one firm in the United States is manufacturing gem spheres from thundereggs. Source: Gemstones, An Overview of Production of Specific U.S. Gemstones: U.S. Bureau of Mines Special Publication 14-95 [ Additional Details and Related Links ]	Click image for additional information.
How large is a lifetime supply of minerals for the average person?
	At today's level of consumption, the average newborn infant will need a lifetime supply of 800 pounds of lead, 750 pounds of zinc, 1,500 pounds of copper, 3,593 pounds of aluminum, 32,700 pounds of iron, 26,550 pounds of clays, 28,213 pounds of salt, and 1,238,101 pounds of stone, sand, gravel, and cement. [ Additional Details and Related Links ]	Click image for additional information.
Does the USGS have reports on the background levels of elements in soils and other surficial materials?
	The following USGS products will be helpful in determining the background levels of various elements in soils and other surficial materials: Professional Paper 1270. Element Concentrations in Soils and Other Surficial Materials of the Conterminous United States, by H.T. Shacklette, and J.G. Boerngen, 1984, 105 p. Digital version of this data can be obtained from David Smith, dsmith@usgs.gov, or call him at (303) 236-1849. Professional Paper 1458. Element Concentrations in Soils and Other Surficial Materials of Alaska, by L.P. Gough, R.C. Severson, and H.T. Shacklette, 1988, 53 p. Digital version of this data can be obtained from David Smith, dsmith@usgs.gov, or call him at (303) 236-1849. [ Additional Details and Related Links ]	Click image for additional information.
What is mine drainage?
	Mine drainage is metal-rich water formed from chemical reaction between water and rocks containing sulfur-bearing minerals. The runoff formed is usually acidic and frequently comes from areas where ore- or coal mining activities have exposed rocks containing pyrite-a sulfur bearing mineral. Metal-rich drainage can also occur in mineralized areas that have not been mined. [ Additional Details and Related Links ]	Click image for additional information.
How does mine drainage occur?
	Mine drainage is formed when pyrite, an iron sulfide, is exposed and reacts with air and water to form sulfuric acid and dissolved iron. Some or all of this iron can precipitate to form the red, orange, or yellow sediments in the bottom of streams containing mine drainage. The acid runoff further dissolves heavy metals such as copper, lead, mercury into ground or surface water. The rate and degree by which acid-mine drainage proceeds can be increased by the action of certain bacteria. [ Additional Details and Related Links ]	Click image for additional information.
What is Marine Geology?
	Geology is the study of the Earth. This scientific study includes how the Earth was formed, how the Earth has changed since it was formed, that materials that make up the earth, and understanding the processes that act on it. Marine Geology focuses these studies in areas affected by our oceans. These are the deep ocean floor, the shallower slopes and shelves that surround the continents, and especially the coasts which include beaches, estuaries, rivers, and large lakes. We study rocks to learn about the materials that make up our Earth. The distribution and properties of these rocks give clues as to how they got there and the processes involved. Why study these things? The materials that we take out of the earth (oil, gas, metals, and other minerals) are vital to our way of life. Understanding where and how much of these resources we have is important in planning our future. Earthquakes, volcanoes, landslides, and hurricanes affect many of us at any moment. Understanding these processes will help to prepare for these events. Learn more about Marine Geology at http://walrus.wr.usgs.gov/pubinfo/margeol.html [ Additional Details and Related Links ]	Click image for additional information.
What research is being conducted to address the acid drainage problem?
	Acid Mine Drainage Status of Research A Science-Based, Watershed Strategy to Support Effective Remediation of Abandoned Mine Lands Use of Tracer Injections and Synoptic Sampling to Measure Metal Loading From Acid Mine Drainage Leadville Mining District Appalachian Clean Streams Initiative Stoneycreek River Acid Mine Drainage Study U.S. Geological Survey Publications Dealing with Acid Mine Drainage Research. [ Additional Details and Related Links ]	Click image for additional information.
What can be done to prevent or clean up mine drainage?
	For more information: Prevention and Mitigation Techniques Treatment Techniques and Costs Acid Mine Drainage Treatment. [ Additional Details and Related Links ]	Click image for additional information.
What is pegmatite?
	A pegmatite is an exceptionally coarse-grained intrusive igneous rock with large interlocking crystals (usually > one inch), typically forming as masses in dikes and veins, especially along the margins of batholiths. A granitic pegmatite has the mineralogy of a granite and abnormally large grains, whereas a gabbroic pegmatite has the mineralogy of a gabbro and very large grains. Pegmatites represent the last and most hydrous magma to crystallize, and sometimes contain rare minerals enriched in the elements boron, lithium, uranium, and rare earths. -- Excerpts from: Margaret O. Plank and William S. Schenck, 1998; Delaware Piedmont Geology: Delaware Geological Survey, University of Delaware, Delaware Geological Survey Website, 2001; British Columbia Ministry of Energy and Mines Website, 2002, and Philip Stoffer, 2002, Rocks and Geology in the San Francisco Bay Region, USGS Bulletin 2195 [ Additional Details and Related Links ]	Click image for additional information.
What are igneous rocks and minerals?
	Igneous rocks (from the Greek word for fire) form from when hot, molten rock (magma) crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface. Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies. Intrusive Igneous Rocks: Intrusive, or plutonic igneous rock forms when magma is trapped deep inside the Earth. Great globs of molten rock rise toward the surface. Some of the magma may feed volcanoes on the Earth's surface, but most remains trapped below, where it cools very slowly over many thousands or millions of years until it solidifies. Slow cooling means the individual mineral grains have a very long time to grow, so they grow to a relatively large size. Intrusive rocks have a coarse grained texture. Extrusive Igneous Rocks: Extrusive, or volcanic, igneous rock is produced when magma exits and cools outside of, or very near the Earth's surface. These are the rocks that form at erupting volcanoes and oozing fissures. The magma, called lava when molten rock erupts on the surface, cools and solidifies almost instantly when it is exposed to the relatively cool temperature of the atmosphere. Quick cooling means that mineral crystals don't have much time to grow, so these rocks have a very fine-grained or even glassy texture. Hot gas bubbles are often trapped in the quenched lava, forming a bubbly, vesicular texture. Pumice, obsidian, and basalt are all extrusive igneous rocks. Volcanic Eruptions: When magma manages to migrate upward onto the surface, the result is volcanism (a volcanic eruption). A volcano forms as molten rock and solidified volcanic debris are ejected onto the surface and accumulate near the eruption site. In addition to rock material, large quantities of water vapor and gases are vented from volcanoes. When magma flows on the surface the material is called lava. The release of pressure during eruptions can produce ash clouds that may travel long distances. Crystallization: When magma cools in the subsurface it slowly forms rock through the process of crystallization. The chemical and physical reactions that take place in cooling magma result in the formation of interlocking mineral crystal grains (minerals such as quartz, feldspar, and mica). The mineral grains (crystals) are of a visible size, giving the rock a crystalline texture. Igneous Rock Classifications: Igneous rocks are classified by the geologic environment where they formed from the crystallization of molten material, and perhaps more importantly, by their mineral composition. Intrusive igneous rocks (like granite or gabbro) typically display visible mineral grains that are fairly easy to recognize with a little training. Extrusive rocks are more difficult to clearly identify because the mineral grains are typically invisible. However, the general composition of an extrusive rock is reflected by its color and density characteristics. General composition types include felsic (which is a mnemonic word derived from "feldspar" and "silica"), and mafic (which means rich in magnesium and iron, Fe). Felsic rocks tend to be light colored (white, pink, yellow), and are typically much less dense than mafic rocks that are typically dark (gray, brown, or black). Mineral Composition: Rhyolite (a felsic extrusive rock) has the same mineral composition as granite (an intrusive igneous rock) and is composed dominantly of the minerals potassium feldspar (K-spar), quartz, and lesser amounts of plagioclase feldspar, mica, hornblende, and other minerals. Likewise, basalt (a mafic extrusive rock) has the same mineral composition of the mafic intrusive rock, gabbro. This generalized composition of felsic and mafic can be subdivided into intermediate (between felsic and mafic composition), and ultramafic (rocks extremely enriched in magnesium and iron). Rocks of intermediate composition include diorite (intrusive) and andesite (the extrusive equivalent). Ultramafic rocks have special significance, in that they probably are derived from the mantle. They are relatively unstable on the Earth's surface, and are typically metamorphosed. In nature and in simplistic interpretation, igneous rocks that make up most continental crust typically have a felsic composition (such as rhyolite and granite). The mafic rock basalt is the dominant rock type that makes up most ocean crust. Rocks of intermediate composition are derived from the mixing of continental and oceanic crust. Batholiths and Other Plutons: A body of rock formed from magma migrating and solidifying deep in the subsurface is called a pluton or an igneous intrusion. Huge intrusions, covering areas greater than one hundred square kilometers are called a batholith. Batholiths typically contain many separate intrusions that form over a relatively long period of time. Other types of intrusions typically form at shallower crustal depths; these include stocks,dikes,and sills. A stock is smaller than a batholith and typically represents the subsurface passage that fed molten material to a volcano or field of volcanoes over time. Sills and dikes are layers of igneous rock that typically form along fault zones, fractures, or between and parallel to sedimentary layers. A laccolith is a blister-shaped intrusion. Stocks, sills, dikes, laccoliths and other intrusions are remnants of past igneous activity and are exposed at the surface long after erosion has stripped away any ancient volcanoes and other overlying rocks and sediments that may have existed in an area. IGNEOUS ROCKS and MINERALS Andesite -- extrusive igneous rock Basalt -- extrusive igneous rock Dacite -- extrusive igneous rock Diabase -- fine-textured igneous rock Diorite -- intrusive igneous rock Gabbro -- intrusive igneous rock Granite -- intrusive igneous rock Granodiorite -- intrusive igneous rock Obsidian -- volcanic glass Olivine -- silicate mineral Pegmatite -- intrusive igneous rock Peridotite -- gem quality olivine Pumice -- light, porous, volcanic rock Rhyolite -- extrusive igneous rock Tuffs -- volcanic ash matrix -- Excerpts from: USGS/NPS Geology in the Parks Website, 2003; and Philip Stoffer, 2002, Rocks and Geology in the San Francisco Bay Region, USGS Bulletin 2195 [ Additional Details and Related Links ]	Click image for additional information.
What is gneiss?
	Gneiss is a coarse-grained, foliated metamorphic rock that commonly has alternating bands of light and dark-colored minerals. [ Additional Details and Related Links ]	Click image for additional information.
What is andesite?
	Andesite is an extrusive igneous rock, light to dark gray, sometimes with reddish to greenish hues; fine-grained, sometimes displays bubbles (vesicular texture), frequently has a brecciated texture (tuff) and sometimes contains phenocrysts of feldspar (Ca and Na rich varieties), quartz, hornblende, pyroxene, and biotite mica. Composition: Andesite is between about 52 and 63 weight percent silica (SiO₂). Andesite crystals are composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende. At the lower end of the silica range, andesite lava may also contain olivine. Stratovolcanoes: Andesite magma commonly erupts from stratovolcanoes as thick lava flows, some reaching several kilometers in length. Andesite magma can also generate strong explosive eruptions to form pyroclastic flows and surges and enormous eruption columns. Andesites erupt at temperatures between 900 and 1,100 degrees C. From the Andes Mountains: The word andesite is derived from the Andes Mountains, located along the western edge of South America, where andesite rock is common. -- Excerpts from: Philip Stoffer, 2002, Rocks and Geology in the San Francisco Bay Region, USGS Bulletin 2195, and USGS Volcano Hazards Website Photoglossary, August 2001 [ Additional Details and Related Links ]	Click image for additional information.
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