Eureka County Nevada, 2007 Minerial Assessment Report

7. GLOSSARY

Aggregate: 1. A mass or body of rock particles, miner grains, or both. 2. Any of several hard, inert materials, such as sand, gravel, slag, or crushed stone, used for mixing with a cementing or bituminous material to form concrete, mortar, or plaster; or used alone, as in railroad ballast or graded fill.

Allochthon: Large block of rock which has been moved (usually long distances) from its original site of formation, usually by low angle thrust faulting (pushed on top of another block of rock).

Alluvial: 1. Pertaining to or composed of alluvium, or deposited by a stream or running water. 2. Said of a placer formed by the action of running water, as in a stream channel or alluvial fan; also, said of the valuable mineral.

Argillite: A compact rock, derived from mudstone or shale, more highly indurated than either of those rocks. It lacks the fissility of shale or the cleavage of slates. It is regarded as a product of weak metamorphism

Barite: An orthorhombic mineral, BaSo4, with a specific gravity of 4.5. It is used in paint and drilling mud, as a filler for paper and textiles, and is the principal ore of barium.

Carbonate: A mineral compound characterized by a fundamental anionic structure. Calcite and aragonite are examples of carbonates. 2. A sediment formed of the carbonates of calcium, magnesium, and/or iron.

Cenozoic: The latest of the four eras into which geologic time is divided; it extends from the close of the Mesozoic Era, about 65 million years ago, to the present. The Cenozoic Era is subdivided into Tertiary and Quaternary periods, or, on a different basis, into Paleogene and Neogene periods.

Chert: A hard, dense microcrystalline or cryptocrystalline sedimentary rock, consisting chiefly of interlocking crystals of quartz less than about 30 um in diameter; it may contain amorphous silica. It has conchoidal fracture, and may be white or variously colored. Chert occurs principally as nodular or concretionary segregations, or nodules, in limestone and dolomite, and less commonly as layered deposits, or bedded chert; it may be an organic or inorganic precipitate or replacement product. The term flint is essentially synonymous.

Clastic: 1. Pertaining to a rock or sediment composed principally of fragments derived from pre-existing rocks or minerals and transported some distance from their places of origin; also said of the texture of such a rock. 2. Pyroclastic 3. Said of a bioclastic rock. 4. Pertaining to the fragments (clasts) composing a clastic rock.

Coal: A readily combustible rock containing more than 50% by weight and more than 70% by volume of carbonaceous material including inherent moisture, formed from compaction and indurations of variously altered plant remains similar to those in peat. Differences in the kinds of plant materials, in degree of metamorphism, and in the range of impurity are sued in classification.

Copper: A reddish or salmon-pink isometric mineral, the native metallic element Cu. It is ductile and malleable, a good conductor of heat and electricity, usually dull and tarnished, and formerly an important ore.

Deformation: 1. A general term for the processes of folding, faulting, shearing, compression, or extension of rocks as a result various earth forces. 2. Strain.

Deposition: 1. The laying-down of rock-forming material by any natural agent. 2. The precipitation of mineral matter from solution.

Devonian: The fourth period of the Paleozoic era. It began 390 million years ago and extended to 340 million years ago.

Diatomaceous Earth: A light colored soft siliceous sedimentary rock, consisting chiefly of opaline frustules of the diatom. Owing to it high surface area, absorptive capacity, and chemical stability, diatomite has a number of uses. The term is generally reserved for deposits of commercial value.

Diatomite: A light colored soft siliceous sedimentary rock, consisting chiefly of opaline frustules of the diatom. Owing to its high surface area, absorptive capacity and chemical stability, diatomite has a number of uses. The term is generally reserved for deposits of commercial value.

Dolomite: 1. A common rock-forming mineral. Part of the magnesium may be replaced by ferrous iron. Dolomite is white to light-colored and has perfect rhombohedral cleavage. 2. A sedimentary rock, of which more than 50% by weight consists of the mineral dolomite; specif. a rock containing more than 90% mineral dolomite and less than 10% calcite. Most dolomite is associated and often interbedded with limestone.

Extrusion: The emission of relatively viscous lava onto the earth's surface; also, the rock so formed.

Extrusive: Said of igneous rock that has been erupted onto the surface of the earth. Extrusive rocks include lava flows and pyroclastic material such as volcanic ash.

Facies: The aspect, appearance, and characteristics of a rock unit, usually reflecting, the conditions of its origin; esp. as differentiating it from adjacent or associated units.

Fault Block: A crustal unit bounded by faults, either completely or in part. It behaves as a unit during faulting and tectonic activity.

Fluorite: A clear to translucent mineral. It is commonly blue or purple, but occurs in many other colors; it is found in cubic crystals and has perfect basal cleavage. Fluorite is a common mineral in vein, is the ore of fluorine, and is used in glass and enamel and in the manufacture of hydrofluoric acid.

Fluorspar: Commercial name for flourite.

Fold: A bend or placation in bedding, foliation, cleavage, or other planar features in rocks. A fold is usually a product of deformation, but the definition does not specify manner of origin. 2. A broad median external undulation or plica on either the dorsal or the ventral valve of a brachiopod.

Formation: 1. A body of rock strata that consists dominantly of a certain lithologic type or combination of types. It is the fundamental lithostratigraphic unit. Formations may be combined into groups or subdivided into members. 2. A lithologicially distinct, mappable body of igneous or metamorphic rock.

Gemstone: A crystalline rock that can be cut and polished for use as a gem.

Geocline: A usually elongate, basinlike depression along the edge of a continent, in which a thick sequence of sediments and volcanic deposits has accumulated

Geothermal: Pertaining to the heat of the interior of the earth.

Gold: A soft yellow mineral, the native metallic element Au. Specific gravity of pure gold is 19.3. It is often naturally alloyed with silver, copper, or other metals, and is found as nuggets and grains in gravels, and in veins associated with quartz.

Graben: An elongate, relatively depressed crustal unit or block that is bounded by faults on its long sides. It is a structural form, which may or may not be geomorphologically expressed as a rift valley.

Gypsum: A widely distributed mineral consisting of hydrous calcium sulfate. It is the commonest sulfate mineral, and if frequently associated with halite and anhydrite in evaporates, forming thick, extensive beds, esp. in rocks of Permian and Triassic age. Gypsum is used mainly as a retard in portland cement, and in making plaster of Paris.

Horst: An elongate, relatively uplifted crustal unit or block that is bounded by faults on its long sides. It is a structural from and may or may not be expressed geomorphologically

Imbricate: Overlapping, as shingles or tiles on a roof.

Intrusion: 1. The process of emplacement of magma in pre-existing rock; magmatic activity. Also, the igneous rock mass so formed. 2. An injection of sedimentary material under abnormal pressure 3. Salt-water encroachment.

Intrusive: Of or pertaining to intrusion, both the process and the rock so formed.

Lacustrine: 1. Pertaining to, produced by, or inhabiting a lake or lakes. 2. Said of a region characterized by lakes.

Limestone: A sedimentary rock consisting chiefly of the mineral calcite (calcium carbonate) with or without magnesium carbonate. Common impurities include chert and clay. Limestone is the most important and widely distributed of the carbonate rocks and is the consolidated equivalent of limy mud, calcareous sand, and/or shell fragments. It yields lime on calcinations.

Lithium: 1. A soft, silvery, highly reactive metallic element that is used as a heat transfer medium and in various alloys, ceramics, and optical forms of glass. 2. Any of several salts of lithium, especially lithium carbonate.

Magma: Naturally occurring molten rock material, generated within the earth and capable of intrusion and extrusion, from which igneous rocks have been derived through solidification and related processes. It may or may not contain suspended solids (such as crystals and rock fragments) and/or gas phases

Magmatic: Of , pertaining to, or derived from magma.

Magnesium: A light silver-white ductile bivalent metallic element; in pure form it burns with brilliant white flame; occurs naturally only in combination (as in magnesite and dolomite and carnallite and spinel and olivine)

Mercury: A heavy, silver-white to tine-white hexagonal mineral, the native metallic element Hg. It is the only metal that is liquid at ordinary temperatures. Native mercury is found as minute fluid globules disseminated through cinnabar (the principal ore of mercury) or deposited from the waters of certain hot springs, but it is unimportant as a source of the metal. It usually contains small amounts of silver. Mercury combines with most metals to form alloys or amalgams. It is highly toxic if breathed or ingested.

Mesozoic: An era of geologic time, from the end of the Paleozoic to the beginning of the Cenozoic, or from about 225 to 65 million years ago; also the rocks formed during that era. It includes the Triassic, Jurassic, and Cretaceous periods.

Metallic: 1. Pertaining to metal. 2. Said of a type of luster that is characteristic of metals.

Mineral: 1. A naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties. Those who include the requirement of crystalline form in the definition would consider and amorphous compound such as opal to be a mineraloid. 2. Any naturally formed inorganic material, i.e. a member of the mineral kingdom as opposed to the plan and animal kingdoms.

Molybdenum: A metallic element that resembles chromium and tungsten in many properties. It is used especially in strengthening and hardening steel, and is a trace element in plant and animal metabolism

Non-metal: 1. A naturally occurring substance that does not have metallic properties such as high luster, conductivity, opaqueness, and ductility. 2. In economic geology, and rock or mineral mined for its nonmetallic value, such as stone, sulfur, or salt.

Non-metallic: 1. Of or pertaining to a nonmetal. 2. Said in general of mineral lusters other than metallic.

Oil Shale: A kerogen-bearing, finely laminated brown or black sedimentary rock that will yield liquid or gaseous hydrocarbons on distillation.

Ordovician: The second period of the Paleozoic era. It began 480 million years ago and extended to 420 million years ago.

Orogeny: Literally, the process of formation of mountains. In present usage, orogeny is the process by which structures within fold-belt mountainous areas were formed, including thrusting, folding, and faulting in the outer and higher layers, and plastic folding, metamorphism, and plutonism in the inner and deeper layers. Only in the very youngest, late Cenozoic mountains is there any evident structure and surface landscape.

Paleontology: The study of life in past geologic time, based on fossil plants and animals in including phylogeny, their relationships to existing plants, animals, and environments, and the chronology of the earth's history.

Paleozoic: An era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic, or from about 570 to about 225 million years ago. Also, the erathem of rocks deposited during the Paleozoic.

Perlite: A natural volcanic glass similar to obsidian but having distinctive concentric cracks and a relatively high water content. In a fluffy heat-expanded form perlite is used as a lightweight aggregate, in fire-resistant insulation, and in soil for potted plants.

Phosphate: A mineral compound containing tetrahedral groups. An example is pyromorphite. Phosphorus, arsenic, and vanadium may substitute for each other in the tetrahedron.

Physiographic Province: A region of which all parts are similar in geologic structure and climate and which has had a unified geomorphic history; its relief features differ significantly from those of adjacent regions

Pleistocene: An epoch of the Quaternary period, after the Pliocene of the Tertiary and before the Holocene; also, the corresponding worldwide series of rocks. It began two to three million years ago and lasted until the start of the Holocene some 8,000 years ago. When the Quaternary is designated as an era, the Pleistocene is considered to be a period.

Pluton: 1. An igneous intrusion. 2. A body of rock formed by metasomatic replacement. - The term originally signified only deep-seated or plutonic bodies of granitoid texture.

Potassium carbonate. &mdash 1. Potassium carbonate. A term loosely used for potassium oxide, potassium hydroxide, or even for potassium in such informal expressions as potash feldspar or potash spar.

Potassium: A soft, silver-white, highly or explosively reactive metallic element that occurs in nature only in compounds. It is obtained by electrolysis of its common hydroxide and found in, or converted to, a wide variety of salts used especially in fertilizers and soaps.

Precambrian: A geologic time, and it corresponding rocks, before the beginning of the Paleozoic; it is equivalent to about 90% of geologic time.

Quaternary: The second period of the Cenozoic era, following the Tertiary; also, the corresponding system of rocks. It began two to three million years ago and extends to the present. It consists of two grossly unequal epochs: the Pleistocene, up to about 8,000 years ago, and the Holocene since that time. The Quaternary may also be incorporated into the Neogene, when the Neogene is designated as a period of the Tertiary era.

Sediment: 1. Solid material that has settled down from a state of suspension in a liquid. 2. More generally, solid fragmental material transported and deposited by wind, water, or ice, chemically precipitated from solution, or secreted by organisms, and that forms in layers in loose unconsolidated from

Sedimentary: Pertaining to or containing sediment, or formed by its deposition.

Shale: A fine-grained detrital sedimentary rock, formed by the compaction of clay, silt, or mud. It has finely laminated structure, which gives it a fissility along which the rock splits readily, especially on weathered surfaces. Shale is well indurated, but not as hard argillite or slate. It may be red, brown, black, or gray.

Siltstone: An indurated silt having the texture and composition of shale but lacking it fine lamination or fissility; a massive mudstone in which silt predominates over clay. It tends to be flaggy, containing hard thin layers, and often showing primary current structures.

Silver: A soft white mineral, the native metallic element Ag. It is often alloyed with small amounts of gold and other elements. It occurs in stringers and veins and in the upper parts of silver-sulfide lodes.

Sodium: Soft, silver-white, metallic element that oxidizes rapidly in moist air, occurring in nature only in the combined state, and used in the synthesis of sodium peroxide, sodium cyanide, and tetraethyllead: a necessary element in the body for the maintenance of normal fluid balance and other physiological functions

Sulfur: An orthorhombic mineral, the native nonmetallic element S. It occurs in yellow crystals at hot springs and fumaroles, and in masses or layers associated with limestone, gypsum, and anhydrite, esp. in salt-dome caprock and bedded deposits.

Tectonic: Pertaining to the forces involved in, or the resulting structures of, tectonics.

Tertiary: The first period of the Cenozoic era (after the Cretaceous of the Mesozoic era and before the Quaternary), thought to have covered the span of time between 65 million and 2 million years ago; also, the corresponding system of rocks. It is divided into five epochs: The Paleocene, Eocene, Oligocene, Miocene, and Pliocene. It was originally designated an era rather than a period; in this sense, it may be considered to have either five periods (Paleocene, Eocene, Oligocene, Miocene, Pliocene) or two (Paleogene and Neogene), with the Pleistocene and Holocene included in the Neogene.

Thrust Fault: A fault with a dip of 45� or less over much of its extent, on which the hanging wall appears to have moved upward relative to the footwall. Horizontal compression rather than vertical displacement is its characteristic feature.

Triassic: The first period of the Mesozoic era (after the Permian of the Paleozoic era, and before the Jurassic), thought to have covered the span of time between 225 and 190 million years ago; also, the corresponding system of rocks. The Triassic is so named because of its threefold division in the rocks of Germany.

Tungsten: A rare, metallic element having a bright-gray color, a metallic luster, and a high melting point, 3410� C, and found in wolframite, tungstite, and other minerals: used in alloys of high-speed cutting tools, electric-lamp filaments, etc.

Uranium: A white, lustrous, radioactive, metallic element, occurring in pitchblende, and having compounds that are used in photography and in coloring glass.

Volcanic Breccia: 1. A pyroclastic rock that consists of angular volcanic fragments that are larger than 64 mm in diameter and that may or may not have a matrix. 2. A rock composed of nonvolcanic fragments in a volcanic matrix.

Volcanic: 1. Pertaining to the activities, structures, or rock types of a volcano. 2. A syn. of extrusive.

Zinc: A ductile, bluish-white metallic element often used in making galvanized iron, brass, and other alloys, and as an element in voltaic cells.