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    The mineral Calcite


















Definitions     A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  














The following was retrieved from Wikipedia, the free encyclopedia :  ( en.wikipedia.org/wiki/Calcite ) on February 26, 2020.

"Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 3 as "calcite".

Other polymorphs of calcium carbonate are the minerals aragonite and vaterite. Aragonite will change to calcite over timescales of days or less at temperatures exceeding 300 °C, and vaterite is even less stable."

Etymology



Calcite is derived from the German Calcit, a term coined in the 19th century from the Latin word for lime, calx (genitive calcis) with the suffix -ite used to name minerals. It is thus etymologically related to chalk.

When applied by archaeologists and stone trade professionals, the term alabaster is used not just as in geology and mineralogy, where it is reserved for a variety of gypsum; but also for a similar-looking, translucent variety of fine-grained banded deposit of calcite.

Properties



Form

Over 800 forms of calcite crystals have been identified. Most common are scalenohedra, with faces in the hexagonal {2 1 1} directions (morphological unit cell) or {2 1 4} directions (structural unit cell); and rhombohedral, with faces in the {1 0 1} or {1 0 4} directions (the most common cleavage plane). Habits include acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms. It may occur as fibrous, granular, lamellar, or compact. A fibrous, efflorescent form is known as lublinite. Cleavage is usually in three directions parallel to the rhombohedron form. Its fracture is conchoidal, but difficult to obtain.

Scalenohedral faces are chiral and come in pairs with mirror-image symmetry; their growth can be influenced by interaction with chiral biomolecules such as L- and D-amino acids. Rhombohedral faces are achiral.

Hardness

It has a defining Mohs hardness of 3, a specific gravity of 2.71, and its luster is vitreous in crystallized varieties. Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, or even black can occur when the mineral is charged with impurities.

Optical

Calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A transparent variety called Iceland spar is used for optical purposes. Acute scalenohedral crystals are sometimes referred to as "dogtooth spar" while the rhombohedral form is sometimes referred to as "nailhead spar".

Single calcite crystals display an optical property called birefringence (double refraction). This strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect (using calcite) was first described by the Danish scientist Rasmus Bartholin in 1669. At a wavelength of ≈590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively. Between 190 and 1700 nm, the ordinary refractive index varies roughly between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4.

Chemical

Calcite, like most carbonates, will dissolve with most forms of acid. Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Although calcite is fairly insoluble in cold water, acidity can cause dissolution of calcite and release of carbon dioxide gas. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. When conditions are right for dissolution, the removal of calcite can dramatically increase the porosity and permeability of the rock, and if it continues for a long period of time may result in the formation of caves. On a landscape scale, continued dissolution of calcium carbonate-rich rocks can lead to the expansion and eventual collapse of cave systems, resulting in various forms of karst topography.

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  Common Minerals



»  Alunite
»  Amphibole
»  Anorthoclase
»  Apatite
»  Azurite
»  Barite
»  Beryl
»  Biotite
»  Bauxite


»  Borax
»  Calcite
»  Carnotite
»  Chalcopyrite
»  Chromite
»  Chrysocolla
»  Cinnabar
»  Corundum
»  Cryolite


»  Cuprite
»  Diamond
»  Dioptase
»  Dolomite
»  Epidote
»  Euclase
»  Feldspar
»  Fluorite
»  Galena


»  Garnet
»  Graphite
»  Gypsum
»  Halite
»  Hematite
»  Hornblende
»  Hydroxylapatite
»  Jadeite
»  Labradorite


»  Leaverite
»  Lepidolite
»  Magnetite
»  Malachite
»  Marcasite
»  Mica
»  Microcline
»  Molybdenite
»  Muscovite


»  Natron
»  Oligoclase
»  Olivine
»  Oregonite
»  Orthoclase
»  Plagioclase
»  Pyrite
»  Quartz
»  Realgar


»  Scheelite
»  Selenite
»  Siderite
»  Simonellite
»  Sphalerite
»  Spinel
»  Stibnite
»  Talc
»  Tanzanite


»  Tellurite
»  Topaz
»  Tourmaline
»  Turquoise
»  Uraninite
»  Wulfenite
»  Zeolite
»  Zircon










  Common Rocks



Igneous :

»  Andesite
»  Basalt
»  Dacite
»  Diorite
»  Gabbro
»  Granite

»  Obsidian
»  Pegmatite
»  Porphyry
»  Pumice
»  Rhyolite
»  Scoria

Sedimentary :

»  Banded iron fm.
»  Breccia
»  Chalk
»  Claystone
»  Coal

»  Conglomerate
»  Coquina
»  Diatomite
»  Evaporite
»  Flint

»  Limestone
»  Marl
»  Mudstone
»  Oil shale
»  Oolite

»  Sandstone
»  Shale
»  Siltstone
»  Travertine
»  Wackestone

Metamorphic :

»  Anthracite
»  Amphibolite
»  Gneiss
»  Marble

»  Quartzite
»  Schist
»  Serpentine
»  Slate










  The Elements



Actinium  89
Aluminum  13
Americium  95
Antimony  51
Argon  18
Arsenic  33
Astatine  85
Barium  56
Berkelium  97
Beryllium  4
Bismuth  83
Bohrium  107
Boron  5
Bromine  35
Cadmium  48


Calcium  20
Californium  98
Carbon  6
Cerium  58
Cesium  55
Chlorine  17
Chromium  24
Cobalt  27
Copernicium  112
Copper  29
Curium  96
Darmstadtium  110
Dubnium  105
Dysprosium  66
Einsteinium  99


Erbium  68
Europium  63
Fermium  100
Flerovium  114
Fluorine  9
Francium  87
Gadolinium  64
Gallium  31
Germanium  32
Gold  79
Hafnium  72
Hassium  108
Helium  2
Holmium  67
Hydrogen  1


Indium  49
Iodine  53
Iridium  77
Iron  26
Krypton  36
Lanthanum  57
Lawrencium  103
Lead  82
Lithium  3
Livermorium  116
Lutetium  71
Magnesium  12
Manganese  25
Meitnerium  109
Mendelevium  101


Mercury  80
Molybdenum  42
Moscovium  115
Neodymium  60
Neon  10
Neptunium  93
Nickel  28
Nihonium  113
Niobium  41
Nitrogen  7
Nobelium  102
Oganesson  118
Osmium  76
Oxygen  8
Palladium  46


Phosphorus  15
Platinum  78
Plutonium  94
Polonium  84
Potassium  19
Praseodymium  59
Promethium  61
Protactinium  91
Radium  88
Radon  86
Rhenium  75
Rhodium  45
Roentgenium  111
Rubidium  37
Ruthenium  44


Rutherfordium  104
Samarium  62
Scandium  21
Seaborgium  106
Selenium  34
Silicon  14
Silver  47
Sodium  11
Strontium  38
Sulfur  16
Tantalum  73
Technetium  43
Tellurium  52
Tennessine  117
Terbium  65


Thallium  81
Thorium  90
Thulium  69
Tin  50
Titanium  22
Tungsten  74
Uranium  92
Vanadium  23
Xenon  54
Ytterbium  70
Yttrium  39
Zinc  30
Zirconium  40























There are currently 118 known chemical elements exhibiting a large number of different physical and chemical properties. Amongst this diversity, scientists have found it useful to use names for various sets of elements, that illustrate similar properties, or their trends of properties. Many of these sets are formally recognized by the standards body IUPAC.

The following collective names are recommended by IUPAC:

Alkali metals – The metals of group 1: Li, Na, K, Rb, Cs, Fr.

Alkaline earth metals – The metals of group 2: Be, Mg, Ca, Sr, Ba, Ra.

Pnictogens – The elements of group 15: N, P, As, Sb, Bi. (Mc had not yet been named when the 2005 IUPAC Red Book was published, and its chemical properties are not yet experimentally known.)

Chalcogens – The elements of group 16: O, S, Se, Te, Po. (Lv had not yet been named when the 2005 IUPAC Red Book was published, and its chemical properties are not yet experimentally known.)

Halogens – The elements of group 17: F, Cl, Br, I, At. (Ts had not yet been named when the 2005 IUPAC Red Book was published, and its chemical properties are not yet experimentally known.)

Noble gases – The elements of group 18: He, Ne, Ar, Kr, Xe, Rn. (Og had not yet been named when the 2005 IUPAC Red Book was published, and its chemical properties are not yet experimentally known.)

Lanthanoids – Elements 57–71: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu,

Actinoids – Elements 89–103: Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr.

Rare-earth metalsSc Y, plus the lanthanoids

Transition elements – Elements in groups 3 to 11 or 3 to 12.






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