Geodes (Greek geoides, "earthlike") are geological rock formations which occur in sedimentary and certain volcanic rocks. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Plate tectonics and hotspots Divergent plate boundaries At the Geodes are essentially rock cavities or vugs with internal crystal formations or concentric banding. Vugs are small to medium-sized cavities inside rock that may be formed through a variety of processes In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating The exterior of the most common geodes is generally limestone or a related rock, while the interior contains quartz crystals and/or chalcedony deposits. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Chalcedony is a Cryptocrystalline form of Silica, composed of very fine intergrowths of the minerals Quartz and Moganite. Other geodes are completely filled with crystal, being solid all the way through. These types of geodes are called nodules. A nodule in Petrology or Mineralogy is a secondary structure generally spherical or irregularly rounded in shape
Geodes can form in any cavity, but the term is usually reserved for more or less rounded formations in igneous and sedimentary rocks, while the more general term "vug" is applied to cavities in fissures and veins. They can form in gas bubbles in igneous rocks, such as vesicles in basaltic lavas, or as in the American Midwest, rounded cavities in sedimentary formations. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Lava is molten rock expelled by a Volcano during an eruption When first expelled from a volcanic vent it is a Liquid at Temperatures After rock surrounding the cavity hardens, dissolved silicates and/or carbonates are deposited on the inside surface. For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI In Chemistry, a carbonate is a salt or Ester of Carbonic acid. Over time, this slow feed of mineral constituents from groundwater or hydrothermal solutions allows crystals to form inside the hollow chamber. Groundwater is Water located beneath the Ground surface in Soil pore spaces and in the Fractures of lithologic formations Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat Bedrock containing geodes eventually weathers and decomposes, leaving them present at the surface if they are composed of resistant material such as quartz.
The size of the crystals, including their form and shade of color, vary—making each geode unique. Some contain clear, pure quartz crystals, and others have rich purple amethyst crystals. Amethyst is a violet variety of Quartz often used as an Ornamental stone in Jewelry. Still others can have agate, chalcedony, or jasper or minerals such as calcite, dolomite, celestite, etc. This article is about the semi-precious stone For other uses see Agate (disambiguation. JasPer is a project to create a reference implementation of the codec specified in the JPEG-2000 Part-1 standard (ie Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Celestine or celestite ( Sr[[Sulfur S]] O 4 is a Mineral consisting of Strontium Sulfate. There is no easy way of telling what the inside of a geode holds until it is cut open or broken apart, however, geodes from any one locality usually have a more restricted variety of interior mineralization.
Geodes are common in some formations in the United States (mainly in Indiana, Iowa, Missouri, Kentucky and Utah). The United States of America —commonly referred to as the The State of Indiana ( was the 19th US state admitted into the union The State of Iowa ( is a state in the Midwestern region of the United States of America. Missouri ( or) is a state in the Midwestern region of the United States bordered by Iowa, Illinois, Kentucky, Tennessee The Commonwealth of Kentucky ( is a state located in the East Central United States of America. The State of Utah (ˈjuːtɔː or) is a western state of the United States. They also are common in Brazil, Namibia and Mexico. |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld Namibia, officially the Republic of Namibia, is a country in Southern Africa on the Atlantic coast The United Mexican States ( or commonly Mexico (ˈmɛksɪkoʊ () is a federal constitutional Republic in North America. A large geode roughly the size of a minivan was discovered in Put-in-Bay, Ohio in the early 20th century. Put-in-Bay is an incorporated village located on South Bass Island, Ottawa County, Ohio, United States. It is known as Crystal Cave, and tours are possible during the summer. The Crystal Cave is a Limestone Cave located in Put-in-Bay Ohio, a small town on South Bass Island in Lake Erie, with walls that In 1967, Iowa designated the geode as the official state rock, and it has a Geode State Park. This is a list of Iowa state parks These State parks of the U
Geodes and geode slices are sometimes dyed with artificial colors. Samples of geodes with unusual colors or highly unlikely formations have usually been synthetically altered.
See also
Sources
- Rocks and Minerals, written by Fredrick H. A concretion is a volume of Sedimentary rock in which a Mineral cement fills the porosity (i A lithophysa (plural lithophysae) is a small cavity found in Felsic Volcanic rocks believed to be caused by expanding gases in Tuffs This article is about a type of rock for the rock and roll band see Thunderegg (band A thunderegg (or thunder egg) is a nodule-like Pough, ISBN 0-395-91096-X
External links
- Geode images, locations and discussion
- Australian Museum Fact sheet
- Utah Geode Beds
- Illinois State Geological Survey. "Geodes—Small Treasure Vaults in Illinois".
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