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Limestone From Wikipedia, the free encyclopedia Jump to: navigation, search For other uses, see Limestone (disambiguation). Limestone Sedimentary Rock Limestone Formation In Waitomo.jpg Limestone in Waitomo District, New Zealand Composition Calcium carbonate: inorganic crystalline calcite and/or organic calcareous material Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera. Limestone makes up about 10% of the total volume of all sedimentary rocks. The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock. Limestone has numerous uses, including as a building material, as aggregate to form the base of roads, as white pigment or filler in products such as toothpaste or paints, and as a chemical feedstock. Description Limestone quarry at Cedar Creek, Virginia, USA La Zaplaz formations in the Piatra Craiului Mountains, Romania. Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Like most other sedimentary rocks, limestone is composed of grains; however, most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts, and extraclasts. These organisms secrete shells made of aragonite or calcite, and leave these shells behind after the organisms die. Limestone often contains variable amounts of silica in the form of chert (chalcedony, flint, jasper, etc.) or siliceous skeletal fragment (sponge spicules, diatoms, radiolarians), and varying amounts of clay, silt and sand (terrestrial detritus) carried in by rivers. Some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i.e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). This produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular (oolite) appearance. The primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, building upon past generations. Below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters (see lysocline). Limestones may also form in both lacustrine and evaporite depositional environments.[1][2] Calcite can be either dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Because of impurities, such as clay, sand, organic remains, iron oxide and other materials, many limestones exhibit different colors, especially on weathered surfaces. Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock. When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly where there are waterfalls, and around hot or cold springs. Calcium carbonate is deposited where evaporation of the water leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls. Coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the mountain building process (orogeny), limestone recrystallizes into marble. Limestone is a parent material of Mollisol soil group. [edit] Classification Two major classification schemes, the Folk and the Dunham, are used for identifying limestone and carbonate rocks. [edit] Folk classification Main article: Folk classification Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks. Based on composition, there are three main components: allochems (grains), matrix (mostly micrite), and cement (sparite). The Folk system uses two-part names; the first refers to the grains and the second is the root. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample.[3] [edit] Dunham classification Main article: Dunham classification The Dunham scheme focuses on depositional textures. Each name is based upon the texture of the grains that make up the limestone. Robert J. Dunham published his system for limestone in 1962; it focuses on the depositional fabric of carbonate rocks. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles. Dunham names are essentially for rock families. His efforts deal with the question of whether or not the grains were originally in mutual contact, and therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of the rock. The Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample.[4] [edit] Types There are many types of limestone the most common ones: Chalk, crystalline, fossilferous, oolitic and travertine. For more see link below. Main article: List of types of limestone [edit] Limestone landscape Main article: Karst topography The Cudgel of Hercules, a tall limestone rock (Pieskowa Skała Castle in the background) Limestone makes up about 10% of the total volume of all sedimentary rocks.[5][6] Limestone is partially soluble, especially in acid, and therefore forms many erosional landforms. These include limestone pavements, pot holes, cenotes, caves and gorges. Such erosion landscapes are known as karsts. Limestone is less resistant than most igneous rocks, but more resistant than most other sedimentary rocks. It is therefore usually associated with hills and downland, and occurs in regions with other sedimentary rocks, typically clays. Karst topography and caves develop in limestone rocks due to their solubility in dilute acidic groundwater. The solubility of limestone in water and weak acid solutions leads to karst landscapes. Regions overlying limestone bedrock tend to have fewer visible above-ground sources (ponds and streams), as surface water easily drains downward through joints in the limestone. While draining, water and organic acid from the soil slowly (over thousands or millions of years) enlarges these cracks, dissolving the calcium carbonate and carrying it away in solution. Most cave systems are through limestone bedrock. Cooling groundwater or mixing of different groundwaters will also create conditions suitable for cave formation. Coastal limestones are often eroded by organisms which bore into the rock by various means. This process is known as bioerosion. It is most common in the tropics, and it is known throughout the fossil record (see Taylor and Wilson, 2003). Bands of limestone emerge from the Earth's surface in often spectacular rocky outcrops and islands. Examples include the Burren in Co. Clare, Ireland; the Verdon Gorge in France; Malham Cove in North Yorkshire and the Isle of Wight,[7] England; on Fårö near the Swedish island of Gotland, the Niagara Escarpment in Canada/United States, Notch Peak in Utah, the Ha Long Bay National Park in Vietnam and the hills around the Lijiang River and Guilin city in China. The Florida Keys, islands off the south coast of Florida, are composed mainly of oolitic limestone (the Lower Keys) and the carbonate skeletons of coral reefs (the Upper Keys), which thrived in the area during interglacial periods when sea level was higher than at present. Unique habitats are found on alvars, extremely level expanses of limestone with thin soil mantles. The largest such expanse in Europe is the Stora Alvaret on the island of Öland, Sweden. Another area with large quantities of limestone is the island of Gotland, Sweden. Huge quarries in northwestern Europe, such as those of Mount Saint Peter (Belgium/Netherlands), extend for more than a hundred kilometers. The world's largest limestone quarry is at Michigan Limestone and Chemical Company in Rogers City, Michigan.[8] [edit] Uses Limestone is very common in architecture, especially in Europe and North America. Many landmarks across the world, including the Great Pyramid and its associated complex in Giza, Egypt, are made of limestone. So many buildings in Kingston, Canada were constructed from it that it is nicknamed the 'Limestone City'.[9] On the island of Malta, a variety of limestone called Globigerina limestone was, for a long time, the only building material available, and is still very frequently used on all types of buildings and sculptures. Limestone is readily available and relatively easy to cut into blocks or more elaborate carving. It is also long-lasting and stands up well to exposure. However, it is a very heavy material, making it impractical for tall buildings, and relatively expensive as a building material. The Great Pyramid of Giza, one of the Seven Wonders of the Ancient World; its outside cover is made entirely from limestone. Courthouse built of limestone in Manhattan, Kansas A limestone plate with a negative map of Moosburg in Bavaria is prepared for a lithography print. Limestone was most popular in the late 19th and early 20th centuries. Train stations, banks and other structures from that era are normally made of limestone. It is used as a facade on some skyscrapers, but only in thin plates for covering, rather than solid blocks. In the United States, Indiana, most notably the Bloomington area, has long been a source of high quality quarried limestone, called Indiana limestone. Many famous buildings in London are built from Portland limestone. Limestone was also a very popular building block in the Middle Ages in the areas where it occurred, since it is hard, durable, and commonly occurs in easily accessible surface exposures. Many medieval churches and castles in Europe are made of limestone. Beer stone was a popular kind of limestone for medieval buildings in southern England. Limestone and (to a lesser extent) marble are reactive to acid solutions, making acid rain a significant problem to the preservation of artifacts made from this stone. Many limestone statues and building surfaces have suffered severe damage due to acid rain. Acid-based cleaning chemicals can also etch limestone, which should only be cleaned with a neutral or mild alkaline-based cleaner. Other uses include: * It is the raw material for the manufacture of quicklime (calcium oxide), slaked lime (calcium hydroxide), cement and mortar. * Pulverized limestone is used as a soil conditioner to neutralize acidic soils. * It is crushed for use as aggregate—the solid base for many roads. * Geological formations of limestone are among the best petroleum reservoirs; * As a reagent in flue gas desulfurization, it reacts with sulfur dioxide for air pollution control. * Glass making, in some circumstances, uses limestone. * It is added to toothpaste, paper, plastics, paint, tiles, and other materials as both white pigment and a cheap filler. * It can suppress methane explosions in underground coal mines. * Purified, it is added to bread and cereals as a source of calcium. * Calcium levels in livestock feed are supplemented with it, such as for poultry (when ground up).[10] * It can be used for remineralizing and increasing the alkalinity of purified water to prevent pipe corrosion and to restore essential nutrient levels.[11] * Used in blast furnaces, limestone extracts iron from its ore. * It is often found in medicines and cosmetics. * It is used in sculptures because of its suitability for carving. [edit] Gallery * Limestone cropping out at São Pedro de Moel beach, Marinha Grande, Portugal * A stratigraphic section of Ordovician limestone exposed in central Tennessee, U.S. The less-resistant and thinner beds are composed of shale. The vertical lines are drill holes for explosives used during road construction. * Thin-section view of a Middle Jurassic limestone in southern Utah. The round grains are ooids; the largest is 1.2 mm in diameter. This limestone is an oosparite. * Photo and etched section of a sample of fossiliferous limestone from the Kope Formation near Cincinnati, Ohio [edit] References 1. ^ Trewin, N.H. & Davidson, R.G. 1999. Lake-level changes, sedimentation and faunas in a Middle Devonian basin-margin fish bed, Geological Society, 156, 535-548 2. ^ Oilfield Glossary: Term 'evaporite' 3. ^ Folk RL, (1974) Petrology of Sedimentary Rocks, Hemphill Publishing, Austin, Texas 4. ^ Dunham, R.J., 1962, Classification of carbonate rocks according to depositional textures, in Ham W.E. (ed.), Classification of carbonate rocks: Am. Assoc. Petroleum Geologists Mem. 1,p. 108-121 5. ^ "Calcite". http://www.mine-engineer.com/mining/mineral/calcite.htm. Retrieved 2008-02-13. 6. ^ "Limestone (mineral)". Archived from the original on 2009-10-31. http://www.webcitation.org/query?id=1257008095152489. Retrieved 2008-02-13. 7. ^ "Isle of Wight, Minerals" (PDF). http://www.iwight.com/council/documents/policies_and_plans/udp/2002_pdfs/minerals.pdf. Retrieved 2006-10-08. 8. ^ Michigan Markers 9. ^ "Welcome to the Limestone City". http://www.citylifeontario.com/kingston/. Retrieved 2008-02-13. 10. ^ "PoultyOne article on Calcium for chickens". http://poultryone.com/articles/calcium.html. 11. ^ "World Health Organization report". http://www.who.int/water_sanitation_health/dwq/nutconsensus/en/. [edit] Further reading * Taylor, P.D. and Wilson, M.A., 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1-103.[1] * Folk RL, (1974) Petrology of Sedimentary Rocks, Hemphill Publishing, Austin, Texas * Dunham, R.J., 1962, Classification of carbonate rocks according to depositional textures, in Ham W.E. (ed.), Classification of carbonate rocks: Am. Assoc. Petroleum Geologists Mem. 1,p. 108-121 [edit] See also Wikimedia Commons has media related to: Limestones * Calcium carbonate * Chalk * Coral sand * In Praise of Limestone Retrieved from "http://en.wikipedia.org/w/index.php?title=Limestone&oldid=456440128" View page ratings Rate this page Rate this page Page ratings What's this? Current average ratings. Trustworthy Objective Complete Well-written I am highly knowledgeable about this topic (optional) I have a relevant college/university degree It is part of my profession It is a deep personal passion The source of my knowledge is not listed here I would like to help improve Wikipedia, send me an e-mail (optional) We will send you a confirmation e-mail. We will not share your address with anyone. (Privacy policy) Submit ratings Saved successfully Your ratings have not been submitted yet Your ratings have expired Please reevaluate this page and submit new ratings. An error has occured. Please try again later. Thanks! Your ratings have been saved. Please take a moment to complete a short survey. Start survey Maybe later Thanks! Your ratings have been saved. Do you want to create an account? An account will help you track your edits, get involved in discussions, and be a part of the community. Create an accountorLog in Maybe later Thanks! Your ratings have been saved. 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What are the scope in geography after graduation? Answer It! In: Professions [Edit categories] Save or Cancel Leica Microsystems Total Digital Pathology Solutions for Health, Research and Education leica-microsystems.com Ads Relevant answers: * Define geography and the nature and scope of geography? Geography is the study of natural and non-natural distribution of things on earth. Geography comes from the Greek meaning drawing of earth. We map out where natural land/ocean resources occur (i.e.... * What is the aim and scope of commercial geography? Commercial geography has assumed an international importance today. The global market has paved a significant scope for a new subject such as Commercial Geography. The etymology of the term itself... * Nature and scope of urban geography? hina * Meaning and scope of commercial geography? it is the study of the way a man adjust their commercial activities to the physical environment.And it is mainly concerned with the study of physical environment,study of agriculture,study of... * Describe resources of geography and it's scope and nature? describe resources Answers.com > Wiki Answers > Categories > Jobs & Education > Jobs > Professions > What are the scope in geography after graduation? HOPG: monochromator &more STM substrate, HOPG x-ray optics, thin films of HOPG and TPG www.optigraph.eu Saybrook Graduate School Earn your MA or PhD at a distance Humanistic Psychology & Org Systems www.saybrook.edu Harvest West Christian Leadership Training Certificate, Diploma and Degree www.harvestwest.edu.au Ads This page is closed to edits. Unfollow follow [report abuse] Can you answer this question? What are the scope in geography after graduation? Read more: http://wiki.answers.com/Q/What_are_the_scope_in_geography_after_graduation#ixzz1bNUh2lrB Copyright © 2011 Answers Corporation

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Petrographic Microscope Petrographic Microscopes. Com is the best informative site the can provide you with loads of information and anything you want to know about petrographic microscopes and other relevant and significant information. This website is purposely designed and created to offer and present comprehensive collection of articles, news and information on petrographic microscopes. Because online shopping is very popular at present, our site provides vast and complete information about petrographic microscopes and other various types of microscopes at just one click. In this way, you can learn more about petrographic microscopes, its applications, specifications and other services before making a decision to purchase. There are various manufacturers that sell their products online and these selling sites are usually linked to this site. Those online shops that deal with selling various kinds of petrographic microscopes are ready to serve you at the best way they can. You can order and purchase petrographic microscopes of your choice, they will be the one to provide fast delivery of the product you ordered and you will pay through pay pal systems that are indicated on the site. However, if you are looking for the right and complete information about petrographic microscopes, you can always log on to our site. The goal of this site is to create outstanding, highly logical and up to date information delivered over the Internet Web. We are committed in providing you with the most interesting articles, news, information and anything you want to know about petrographic microscopes and other relevant information. Our mission is to create comprehensive articles on the Internet. We employ highly qualified article writers and web designers to ensure the excellent presentation of our websites. Review our site and find anything and everything you want to know about petrographic microscopes and other relevant information. We guarantee that our site only provides articles, news and information that are reliable, comprehensive and outstanding. Our site is the best informative site among others. We are looking forward to serve you best and to offer you with the most comprehensive and broad information about petrographic microscopes and other relevant topics. Everything you want to know about the latest news and information on orthopedic tools, you can find it here in our site. I recommend that you review our site to find more and learn more interesting information. Call our Sales Hotline at 1-877-2384-3931 or Email sales@petrographicmicroscope.com 40x 600x Infinity Corrected Polarizing Trinocular Microscope W/ Case + Mineral Slides Set W/ USB Jpg Image Digital Camera W/ Live Motion Video CCD Camera 40X - 600X INFINITY CORRECTED POLARIZING TRINOCULAR MICROSCOPE W/ CASE + MINERAL SLIDES SET W/ USB JPG IMAGE DIGITAL CAMERA W/ LIVE MOTION VIDEO CCD CAMERA Discounted from actual price below. 40x 630x Compound Trinocular Polarizing Geological Microscope W/ Case + Mineral Slides Set USB Jpg Image Digital Camera W/ Live Motion Video CCD Camera 40X - 630X COMPOUND TRINOCULAR POLARIZING GEOLOGICAL MICROSCOPE W/ CASE + MINERAL SLIDES SET USB JPG IMAGE DIGITAL CAMERA W/ LIVE MOTION VIDEO CCD CAMERA Discounted from actual price below. 40x 400x Compound Monocular Polarizing Geological Microscope W/ Bertrand Lens 40X - 400X COMPOUND MONOCULAR POLARIZING GEOLOGICAL MICROSCOPE W/ BERTRAND LENS Discounted from actual price below. Click here to view other Petrographic Microscope Products. Click Here For Online Chat Support Skilled Microscopist Available Now to Chat. Please click here if you don't get through on our phones. * 40X - 600X INFINITY CORRECTED POLARIZING TRINOCULAR MICROSCOPE W/ CASE + MINERAL SLIDES SET W/ USB JPG IMAGE DIGITAL CAMERA W/ LIVE MOTION VIDEO CCD CAMERA * 40X - 630X COMPOUND TRINOCULAR POLARIZING GEOLOGICAL MICROSCOPE W/ CASE + MINERAL SLIDES SET USB JPG IMAGE DIGITAL CAMERA W/ LIVE MOTION VIDEO CCD CAMERA * 40X - 400X COMPOUND MONOCULAR POLARIZING GEOLOGICAL MICROSCOPE W/ BERTRAND LENS * 40X - 400X COMPOUND TRINOCULAR POLARIZING GEOLOGICAL MICROSCOPE W/ BERTRAND LENS * 40X - 400X MONOCULAR ORE ROCK POLARIZING PETROGRAPHIC MICROSCOPE THIN THICK OPAQUE SPECIMEN POLARIZED TRANSMITTED LIGHT POLARIZED INCIDENT LIGHT Petrographic Microscope Contact Details Affiliated Sites: * Metallurgical Microscope * Student Microscope * Fluorescence Microscope * Measuring Microscope * Dissecting Microscope * Cheap Microscope * Field Microscope * Stereo Zoom Microscope * Toy Microscope * Gemological Microscope * USB Microscope * Inspection Microscope * USB Digital Microscope * Medical Microscope * Teaching Microscope * Tissue Culture Microscope * Blood Microscope * Shop Microscope * Optical Microscope * School Microscope * Polarizing Microscope * Comparison Microscope * Phase Contrast Microscope Home | About Us | Products | Resources | Articles | Contact Us Copright 2007 Petrographic Microscope. All Rights Reserved.

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The Zeolite Group of Minerals The Zeolites are a popular group of minerals for collectors and an important group of minerals for industrial and other purposes. They combine rarity, beauty, complexity and unique crystal habits. Typically forming in the cavities (or vesicles) of volcanic rocks, zeolites are the result of very low grade metamorphism. Some form from just subtle amounts of heat and pressure and can just barely be called metamorphic while others are found in obviously metamorphic regimes. Zeolite crystals have been grown on board the space shuttle and are undergoing extensive research into their formation and unique properties. The zeolites are framework silicates consisting of interlocking tetrahedrons of SiO4 and AlO4. In order to be a zeolite the ratio (Si +Al)/O must equal 1/2. The alumino-silicate structure is negatively charged and attracts the positive cations that reside within. Unlike most other tectosilicates, zeolites have large vacant spaces or cages in their structures that allow space for large cations such as sodium, potassium, barium and calcium and even relatively large molecules and cation groups such as water, ammonia, carbonate ions and nitrate ions. In the more useful zeolites, the spaces are interconnected and form long wide channels of varying sizes depending on the mineral. These channels allow the easy movement of the resident ions and molecules into and out of the structure. Zeolites are characterized by their ability to lose and absorb water without damage to their crystal structures. The large channels explain the consistent low specific gravity of these minerals. Zeolites have many useful purposes. They can perform ion exchange, filtering, odor removal, chemical sieve and gas absorption tasks. The most well known use for zeolites is in water softeners. Calcium in water can cause it to be "hard" and capable of forming scale and other problems. Zeolites charged with the much less damaging sodium ions can allow the hard water to pass through its structure and exchange the calcium for the sodium ions. This process is reversable. In a similar way zeolites can absorb ions and molecules and thus act as a filter for odor control, toxin removal and as a chemical sieve. Zeolites can have the water in their structures driven off by heat with the basic structure left intact. Then other solutions can be pushed through the structure. The zeolites can then act as a delivery system for the new fluid. This process has applications in medicine, livestock feeds and other types of research. Zeolites added to livestock feed have been shown to absorb toxins that are damaging and even fatal to the growth of the animals, while the basic structure of the zeolite is biologically neutral. Aquarium hobbyists are seeing more zeolite products in pet stores as zeolites make excellent removers of ammonia and other toxins. Most municipal water supplies are processed through zeolites before public consumption. These uses of zeolites are extremely important for industry, although synthetic zeolites are now doing the bulk of the work. Zeolites have basically three different structural variations. --> * There are chain-like structures whose minerals form acicular or needle-like prismatic crystals, ie natrolite. * Sheet-like structures where the crystals are flattened platy or tabular with usually good basal cleavages, ie heulandite. * And framework structures where the crystals are more equant in dimensions, ie Chabazite. A zeolite can be thought of in terms of a house, where the structure of the house (the doors, windows, walls and roof) is really the zeolite while the furniture and people are the water, ammonia and other molecules and ions that can pass in and out of the structure. The chain-like structures can be thought of like towers or high wire pylons. The sheet-like structures can be thought of like large office buildings with the sheets analogous to the floors and very few walls between the floors. And the framework structures like houses with equally solid walls and floors. All these structures are still frameworks (like the true tectosilicates that zeolites are). These variations make the zeolite group very diverse, crystal habit-wise. Otherwise zeolites are typically soft to moderately hard, light in density, transparent to translucent and have similar origins. There are about 45 natural minerals that are recognized members of the Zeolite Group. Industrially speaking, the term zeolite includes natural silicate zeolites, synthetic materials and phosphate minerals that have a zeolite like structure. The complexity of this combined group is extensive with over 120 structural variations and more are being discovered or made every year. Collecting zeolites can be very enjoyable and fulfilling. These are the members of the Zeolite Group: * The Analcime Family: o Analcime (Hydrated Sodium Aluminum Silicate) o Pollucite (Hydrated Cesium Sodium Aluminum Silicate) o Wairakite (Hydrated Calcium Sodium Aluminum Silicate) * Bellbergite (Hydrated Potassium Barium Strontium Sodium Aluminum Silicate) * Bikitaite (Hydrated Lithium Aluminum Silicate) * Boggsite (Hydrated calcium Sodium Aluminum Silicate) * Brewsterite (Hydrated Strontium Barium Sodium Calcium Aluminum Silicate) * The Chabazite Family: o Chabazite (Hydrated Calcium Aluminum Silicate) o Willhendersonite (Hydrated Potassium Calcium Aluminum Silicate) * Cowlesite (Hydrated Calcium Aluminum Silicate) * Dachiardite (Hydrated calcium Sodium Potassium Aluminum Silicate) * Edingtonite (Hydrated Barium Calcium Aluminum Silicate) * Epistilbite (Hydrated Calcium Aluminum Silicate) * Erionite (Hydrated Sodium Potassium Calcium Aluminum Silicate) * Faujasite (Hydrated Sodium Calcium Magnesium Aluminum Silicate) * Ferrierite (Hydrated Sodium Potassium Magnesium Calcium Aluminum Silicate) * The Gismondine Family: o Amicite (Hydrated Potassium Sodium Aluminum Silicate) o Garronite (Hydrated Calcium Aluminum Silicate) o Gismondine (Hydrated Barium Calcium Aluminum Silicate) o Gobbinsite (Hydrated Sodium Potassium Calcium Aluminum Silicate) * Gmelinite (Hydrated Sodium Calcium Aluminum Silicate) * Gonnardite (Hydrated Sodium Calcium Aluminum Silicate) * Goosecreekite (Hydrated Calcium Aluminum Silicate) * The Harmotome Family: o Harmotome (Hydrated Barium Potassium Aluminum Silicate) o Phillipsite (Hydrated Potassium Sodium Calcium Aluminum Silicate) o Wellsite (Hydrated Barium Calcium Potassium Aluminum Silicate) * The Heulandite Family: o Clinoptilolite (Hydrated Sodium Potassium Calcium Aluminum Silicate) o Heulandite (Hydrated Sodium Calcium Aluminum Silicate) * Laumontite (Hydrated Calcium Aluminum Silicate) * Levyne (Hydrated Calcium Sodium Potassium Aluminum Silicate) * Mazzite (Hydrated Potassium Sodium Magnesium Calcium Aluminum Silicate) * Merlinoite (Hydrated Potassium Sodium Calcium Barium Aluminum Silicate) * Montesommaite (Hydrated Potassium Sodium Aluminum Silicate) * Mordenite (Hydrated Sodium Potassium Calcium Aluminum Silicate) * The Natrolite Family: o Mesolite (Hydrated Sodium Calcium Aluminum Silicate) o Natrolite (Hydrated Sodium Aluminum Silicate) o Scolecite (Hydrated Calcium Aluminum Silicate) * Offretite (Hydrated Calcium Potassium Magnesium Aluminum Silicate) * Paranatrolite (Hydrated Sodium Aluminum Silicate) * Paulingite (Hydrated Potassium Calcium Sodium Barium Aluminum Silicate) * Perlialite (Hydrated Potassium Sodium Calcium Strontium Aluminum Silicate) * The Stilbite Family: o Barrerite (Hydrated Sodium Potassium Calcium Aluminum Silicate) o Stilbite (Hydrated Sodium Calcium Aluminum Silicate) o Stellerite (Hydrated Calcium Aluminum Silicate) * Thomsonite (Hydrated Sodium Calcium Aluminum Silicate) * Tschernichite (Hydrated Calcium Aluminum Silicate) * Yugawaralite (Hydrated Calcium Aluminum Silicate) Zeolites have many "cousins" or minerals that have similar cage-like framework structures or have similar properties and/or are associated with zeolites; but are not zeolites, at least as defined mineralogically. These include the phosphates: kehoeite, pahasapaite and tiptopite; and the silicates: hsianghualite, lovdarite, viseite, partheite, prehnite, roggianite, apophyllite, gyrolite, maricopaite, okenite, tacharanite and tobermorite. It is interesting to compare these minerals to the zeolites. Can your phone read QR-Codes? [QR Codes can be read by any iPhone, Droid, Blackberry (v5+), and many others including 90% of phones sold in Japan!] QR-MESSAGES.COM Copyright ©1995-2011 by Amethyst Galleries, Inc. Site design & programming by galleries.com web services

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Struktur kristal Dalam mineralogi dan kristalografi, struktur kristal adalah suatu susunan khas atom-atom dalam suatu kristal. Suatu struktur kristal dibangun oleh sel unit, sekumpulan atom yang tersusun secara khusus, yang secara periodik berulang dalam tiga dimensi dalam suatu kisi. Spasi antar sel unit dalam segala arah disebut parameter kisi. Sifat simetri kristalnya terwadahi dalam gugus spasinya. Struktur dan simetri suatu emmainkan peran penting dalam menentukan sifat-sifatnya, seperti sifat pembelahan, struktur pita listrik, dan optiknya. Sel unit Satu sel unit adalah susunan spatial atom-atom yang mengekor secara tiga dimensi untuk menggambarkan kristalnya. Posisi atom dalam sel unit digambarkan sebagai unit asimetri atau basis, sekumpulan posisi atom (xi,yi,zi) yang diukur dari suatu titik kisi. Setiap struktur kristal memiliki sel unit konvensional yang biasanya dipilih agar kisi yang dihasilkan sesimetris mungkin. Meski begitu, sel unit konvensional tidak selalu pilihan terkecil yang mungkin. Suatu sel unit primitif dari suatu struktur kristal merupakan sel unit terkecil yang mungkin yang dapat dibangun, sehingga, ketika disusun, akan mengisi spasi/ruang secara sempurna. Sel Wigner-Seitz adalah suatu sel primitif khas yang memiliki simetri yang sama dengan kisinya. [sunting] Sistem kristal [sunting] Klasifikasi kisi [sunting] Kisi atom raksasa Suatu kisi kristal yang terdiri dari atom yang saling berikatan dengan ikatan kovalen, misalnya, intan. Zat dengan kisi atomik raksasa sangat kuat serta mempunyai titik leleh dan didih yang sangat tinggi. [sunting] Kisi ion raksasa Suatu kisi kristal yang terdiri dari ion yang terikat satu sama lain dengan ikatan ion, misalnya, natrium klorida. Ikatan ion sangat kuat, ini berarti zat akan mempunyai titik leleh dan titik didih yang tinggi. [sunting] Kisi logam raksasa Suatu kisi kristal yang terdiri dari atom logam yang saling berikatan dengan ikatan logam, misalnya, zink. Elektron terdelokalisasi bebas bergerak, menjadikan logam penghantar listrik dan panas yang baik. Lapisan logam dapat saling melipat di atas yang lain, membuat logam dapat ditempa dan dapat ditarik. [sunting] Kisi molekular Suatu kisi kristal yang terdiri dari molekul yang saling berikatan dengan gaya-gaya antarmolekul, misalnya, iodin. Gaya ini lemah, sehingga kristal mempunyai titik leleh dan didih yang rendah bila dibandingkan dengan senyawa ion dan dapat dengan mudah diputuskan. Ikatan kovalen di dalam molekulnya lebih kuat dan tidak terlalu mudah untuk diputuskan.[1] [sunting] Lihat pula * Kristal * Kristalografi * Kerusakan kristalografis * Pertumbuhan kristal * Kristal cair * Pembelahan (kristal) Untuk embaran lebih rinci mengenai penerapan teknologi yang spesifik, lihat rekayasa bahan, ilmu bahan, keramik, metalurgi, atau fisika bahan. [sunting] Referensi 1. ^ Wertheim, Jane; Oxlade, Chris; Stockley, Corinne. Kamus Kimia Bergambar. Diterjemahkan oleh Dra. Agusniar Trisnamiati, M.Si. Jakarta: Erlangga, 2004. ISBN 9796884895 Teks tersedia di bawah Lisensi Atribusi/Berbagi Serupa Creative Commons; ketentuan tambahan mungkin berlaku. Lihat Ketentuan Penggunaan untuk lebih jelasnya.

Penggunaan Briket Batubara sebagai Sumber Energi Alternatif

Penduduk Indonesia yang bergolongan ekonomi menengah ke bawah masih cukup banyak yang menggunakan minyak tanah sebagai bahan bakar untuk menjalankan kehidupan kesehariannya. Padahal, harga minyak bumi yang beberapa tahun terakhir ini sangat bergejolak dan cenderung mengalami trend kenaikan harga membuat harga minyak tanahpun semakin meningkat. Berbagai sumber energi alternatif pengganti BBM tentunya sangat diperlukan dalam rangka menghadapi kondisi ini. Salah satu energi alternatif untuk kebutuhan memasak yang berpotensi bagi penduduk ekonomi menengah ke bawah adalah briket batubara. Walaupun cadangan batubara di Indonesia relatif besar, sebagian besar sumber daya batubatra tersebut merupakan batubara berperingkat rendah yang berkadar air tinggi. Batubara berperingkat rendah akan cocok untuk berbagai kebutuhan rumah tangga dan industri kecil, misalnya memasak. Oleh karena itu, bentuk briket merupakan bentuk paling cocok sebagai sumber energi alternatif memasak di kegiatan rumah tangga. Selanjutnya, perbandingan analisis ekonomi pada investasi dan pengeluaran saat menggunakan minyak tanah, elpiji, dan briket batubara akan diperlihatkan. Berbagai asumsi yang dipakai dalam analisis ekonomi ini adalah sebagai berikut: 1. Investasi awal untuk penggunaan minyak tanah dan briket batubara adalah berupa kompor 2. Investasi awal untuk penggunaan elpiji adalah berupa kompor gas, regulator, dan tabung elpiji 3 kg. 3. Harga dari minyak tanah dan elpiji adalah harga yang ditetapkan oleh PT Pertamina sebagai bahan bakar bersubsidi 4. Harga briket batubara merupakan harga nyata di daerah Bandung, Jawa Barat (di tingkat pengecer) 5. Lama penggunaan bahan bakar : 2 jam/hari Setelah sekitar 6 bulan pemakaian briket batubara, pengguna briket diprediksi sudah mampu menekan pengeluaran total dibandingkan jika menggunakan bahan bakar minyak tanah atau elpiji. Penggunaan bahan bakar elpiji relatif mahal di awal karena investasi peralatannya relatif lebih mahal dibandingkan yang lain. Penggunaan elpiji baru akan ekonomis saat bahan bakar ini digunakan dalam jangka waktu yang panjang. Dalam jangka waktu 1 tahun, diperlihatkan bahwa baik elpiji maupun briket batubara sudah mampu memberikan penghematan jika dibandingkan dengan penggunaan minyak tanah yang masih banyak digunakan sekarang untuk memasak. Analisis ekonomi dengan berbagai asumsi kasar di atas ini menunjukkan adanya potensi keekonomisan penggunaan bahan bakar alternatif briket batubara dalam menggantikan minyak tanah saat ini. CARA MEMBUAT BRIKET DARI LIMBAH PERTANIAN : Limbah pertanian seperti kulit kacang, bonggol jagung, dan tempurung kelapa bisa diolah menjadi briket. Di tengah rencana pemerintah menaikkan harga elpiji, briket bisa menjadi bahan bakar alternatif. Setiap 1 kilogram briket bisa menghasilkan panas hingga 1,5 jam. Dengan harga Rp 2.500 per kg, biaya lebih hemat dibandingkan dengan elpiji. ”Menggunakan elpiji, panas 1,5 jam butuh biaya Rp 7.000,” kata Edi Gunarto, perajin briket di Dusun Plebengan, Sidomulyo, Bambanglipuro, Bantul, Selasa (30/11). Dalam sehari, ia memproduksi 100 kg briket. Untuk briket sebanyak itu, dia butuh bahan baku kulit kacang tanah dan bonggol jagung 200 kg. Produksi briketnya selalu habis diserap pasar, terutama industri rumah tangga. Di kalangan industri rumah tangga, briket menjadi bahan bakar alternatif murah dibandingkan dengan elpiji atau batubara. ”Mayoritas pelanggan kami usaha katering, batik, dan industri makanan dan minuman yang butuh pembakaran,” ujarnya. Briket belum banyak diminati konsumen rumah tangga. Kebiasaan siap pakai dan kepraktisan membuat warga memilih elpiji. ”Briket harus digunakan sampai nyala apinya habis, sementara di rumah tangga pemakaiannya tak menentu. Kami sedang mendesain kompor tungku yang bisa digunakan praktis,” katanya. Pembuatan briket diawali pembakaran bahan baku di drum selama dua jam. Setelah dingin, bahan itu lalu dihancurkan hingga menjadi serbuk dan dicampur tepung kanji dengan perbandingan 10:1. Proses terakhir adalah cetak briket dengan mesin. Novi Setiawan, perajin briket di Jurug, Bangunharjo, Sewon, mengatakan, tempurung kelapa juga bisa jadi briket. Harga jualnya jauh lebih tinggi, yakni Rp 7.350 per buah. Briket lainnya Rp 2.000-Rp 2.500 per buah. Daya tahan panas yang lebih lama menjadi alasan utama. Briket lebih banyak diekspor. Namun, fluktuatif. ”Kami mulai melirik lokal, terutama industri rumah tangga,” ujarnya. KESIMPULANYA Berbagai sumber energi alternatif pengganti BBM tentunya sangat diperlukan dalam rangka menghadapi kondisi ini. Salah satu energi alternatif untuk kebutuhan memasak yang berpotensi bagi penduduk ekonomi menengah ke bawah adalah briket batubara. Dan analisis ekonomi dengan berbagai asumsi kasar di atas ini menunjukkan adanya potensi keekonomisan penggunaan bahan bakar alternatif briket batubara dalam menggantikan minyak tanah saat ini. KOMPAS.com © 2008 – 2011

http://www.geologynet.com

Magazine Corner Earth Science and Related Magazines and Journals Links to General Interest Earth Science and Related Magazines Click on the Magazine Title for More Information Dedicated Earth Science Magazines and Journals General Science Magazines and Journals Other Sites Earth Science Journals - List of Online Journals Mining Journals and Publications - Goldsheet Web Site Dedicated Earth Science Magazines and Journals Computers and Geosciences See Online MagazineDescription Computers and Geosciences is a journal devoted to all aspects of computing in the geosciences. It brings to its readers information about databases, data structures, computer graphics, numerical methods, simulation models, statistical and expert system methods, image analysis, spatial analysis and other topics of interest to geoscientists working with computers. The term `geoscience' is used in its broadest sense. Online. See all Elsevier Science Journals European Journal of Mineralogy See Online Magazine Description The European Journal of Mineralogy (EJM) was founded in 1988 to reach a large audience on an international scale and also for achieving closer cooperation of European countries in the publication of scientific papers. EJM publishes original papers, review articles and short notes dealing with all mineralogical sciences, which include primarily mineralogy, petrology, geochemistry, crystallography and ore geology, as well as applied and technical mineralogy or any related field. Online Abstracts. Earth and Planetary Science Letters See Online Magazine Description Earth and Planetary Science Letters and thus EPSL Online covers research into all aspects of plate tectonics, ocean-floor spreading and continental drift, as well as basic studies of the physical, chemical and mechanical properties of the earth's crust and mantle, the atmosphere and the hydrosphere. 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News and Briefing columns report on news from the geological community, recent research that has appeared in the specialist journals, geological happenings and discoveries and geological conferences. Fossils Explained and Minerals Explained are two regular series looking at the origins, classification and identification of fossils and minerals. A lively Correspondence section allows readers to air and share their views and to respond to items appearing in the journal. This melting pot of news, views and opinion makes fascinating reading. See all Blackwell Science Journals Geoscience World See Online Magazine Description GeoScienceWorld (GSW) is a nonprofit corporation formed by a group of leading geoscientific organizations for the purpose of making geoscience research and related information easily and economically available via the Internet. GSW is an unprecedented collaboration of six leading earth science societies and one institute. The Founding Organizations: * American Association of Petroleum Geologists (AAPG), * American Geological Institute (AGI), * Geological Society of America (GSA), * The Geological Society of London (GSL), * Mineralogical Society of America (MSA), * Society for Sedimentary Geology (SEPM), and * Society of Exploration Geophysicists (SEG) These Founders have worked together with other geoscience societies and university presses to develop an electronic research resource that is unprecedented in our field of science. Initially, GeoScienceWorld (GSW) will deliver online the aggregated journal content of the Founding Organizations and of other not-for-profit and independent geoscience publishers. With time, other material such as maps, books, and geoscience digital data will be included or inter-linked. When technically practical, GSW will include non-English publications. geotimes.gif (28374 bytes) Geotimes See Online Magazine Description A Publication of the American Geological Institute. Covers news, politics, people and places in geosciences mainly related to American Geological Institute Members. Online notes. GSA Today See Online Magazine Description Welcome to GSA Today, the monthly newsmagazine of the Geological Society of America. This publication is provided in print to all members of GSA as part of their dues, and is available to others on an annual subscription basis (E-mail pubs@geosociety.org for information and rates). Full Articles Online. Mineralogical Record See Online Magazine Description The principal product of the Mineralogical Record Inc. is the Mineralogical Record magazine, issued six times a year. This is the most authoritative and widely respected collector's journal in the world; no serious advanced mineral collector would be without it, and over the years many beginners to the field have learned from it the critical and extensive information they need to go from novice to expert to connoisseur. Copies of the magazine are never discarded like old newspapers, but are carefully saved and collected as reference works of permanent value. Table of Contents covering all assues online. Petroleum Data Manager See Online Magazine Description The Data Room was founded in 1995 with the objective of providing consultancy, training and services in the field of E&P data management. Neil McNaughton, president of The Data Room is an explorationist with over 20 years experience of managing and exploiting E&P data and is a member of the following societies:- SEG, EAGE, AFTP, ARMA, AAPG and SPE. Most recently, The Data Room's reputation for lucid and penetrating analysis of high tech subjects has led to its being selected by an international organisation for a major study of the evolution of international telecommunications markets. 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Here you'll find articles and resources of interest to professional and avocational collectors, beginners, children, and educators. All content is available online for free viewing. Online. Discover See Online Magazine Description Discover is an award-winning, clearly written general interest magazine devoted to the world of science and technology. It intelligently explores all areas of science — from archaeology to ecology, technology to medicine, and astronomy to physics. Each issue uncovers the latest breakthroughs on such intriguing subjects as the origin of life, the evolution of the universe, the inner workings of the human brain, and the mass extinction of the dinosaurs. National Geographic World and National Geographic See Online Magazine Description National Geographic World is a colorful monthly publication that targets junior member, aged 8-14, of the National Geographic Society. Features encourage readers to protect the planet's resources and to learn more about geography, adventure, wildlife, science, and youngsters of special distinction from around the world. Educational games, puzzles, and quizzes complete this captivating journal. Natural History See Online Magazine Description Natural History magazine translates the natural sciences into fascinating reading and spectacular color photography. From anthropology to zoology, the inner man to outer space, Natural History's articles are engrossing and easy to understand. The magazine is a unique combination of visual beauty and scientific accuracy that explores, defines, and depicts. Each issue is an adventure you won't want to miss. Nature See Online Magazine Description Nature appears weekly and publishes papers from any area of science with great potential impact. The importance of Nature papers often extends well beyond the confines of the specific discipline concerned. (Nature's "impact factor", measured by the independent organization the Institute of Scientific Information in Philadelphia, is higher than any other interdisciplinary scientific journal.) Nature also publishes a broad range of informal material in the form of Opinion articles, News stories, Briefings and Recruitment features, and contributed material such as Correspondence; Commentary; News and Views; Scientific Correspondence; book, software and product reviews; Reviews; Progress articles; etc. Popular Science See Online Magazine Description Popular Science is the what's new magazine of science and technology. Each issue covers the latest developments in cars, electronics, communications, tools, energy, aviation, science, space exploration, and much more. Science News See Online Magazine Description Science News is published weekly and is tailored to science professionals and others interested in science, medicine, and technology. 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