Ópalo

Características generales

Fórmula: SiO₂·nH₂O
Sistema de cristalización: Amorfo
Lustre: Vítreo plomizo
Color: Yellow, white, red, brown or blue
Dureza: 5,5-6,5
Rareza: extendido
Características distintivas: Colour play (opalescent), low density, lack of cleavage and crystal faces and fracture filling tendency.

Clasificación

Estado IMA: Válido. Descrito con antelación a 1959 (pre-IMA), se considera un mineral clásico o histórico (grandfathered)

Nickel-Strunz : 04.DA.10

4: Óxidos
04.D: Metal:Oxígeno = 1:2 y similar
04.DA: Con cationes pequeños: Familia de la sílice

Dana 8th ed. : 75.2.1.1

Formación y ambiente

Sedimentary and secondary from the alteration of high silica igneous extrusive rocks.

Accessory, extrusive, hydrothermal (low temp), igneous, magmatic (ultra-basic), metamorphic (hydrothermal), secondary, sedimentary, weathering crusts

Propiedades fisicas

Hábito: Stalactitic, reniform, massive or amorphous

Lustre: Vítreo plomizo

Transparencia: Transparente, Opaco

Color: Yellow, white, red, brown or blue

Color en sección fina: Incolora

Raya: Blanco

Dureza (Mohs): 5,5-6,5

Fractura: Concoidal

Densidad: 1,9-2,3 g/cm³ (medida)

Cristalografía

Sistema cristalino:

Amorfo

Clase (H-M): 0m () - Indefinida

Propiedades ópticas

Tipo: Isotrópico

Valores RI: n_α= 1,43

Dispersión: Ninguna

Propiedades químicas

Fórmula: SiO₂·nH₂O

Elementos químicos: Si, O, H

Composición química: H2O: 20,66%, H: 3,47%, Si: 32,24%, O: 64,29%,

Tests químicos

Fusibilidad: 7; Mineral tipo: Cuarzo; Punto de fusión: 1710ºC; Infusible con soplete
Reacción a los ácidos: Se disuelve en HF
Ensayos en tubo abierto: Becomes dull and cracks.
Ensayos en tubo cerrado: Gives off water.
Formación de sublimados: Infusible.

Otras propiedades

Fluorescente (LW): White
Fluorescente (SW): Greenish yellow
Luminiscente: Yellow-white, yellow-green, white or green
: Green or brown
Magnetismo: No magnético

Relaciones con otros minerales

Minerales acompañantes

Mineral	Fórmula	Sistema	Dureza	Color	Raya	Brillo
Calcedonia	SiO₂	6.5-7	Incoloro, blanco, gris,...	Blanco	Vítreo
Cristobalita	SiO₂	Tetragonal	6-7	Blanco	Vítreo
Nontronita	Na_0.3Fe₂((Si,Al)₄O₁₀)(OH)₂·nH₂O	Monoclínico	1,5-2	Blanco	Terroso
Cuarzo	SiO₂	Trigonal	7	Blanco, transparente. Según variación también puede ser rosa, rojizo o negro.	Blanco	Vítreo
Sepiolita	Mg₄(Si₆O₁₅)(OH)₂·6H₂O	Ortorrómbico	2-2,5	Gris, blanco verde azulado, blanco grisáceo, blanco rojizo, blanco amarillento	Blanco	Terroso

Yacimientos y localidades de interés

Localidades

Burra Burra mine, Burra, South Australia, Australia
Coober Pedy, South Australia, Australia
Cygnet, Tasmania, Australia
Lightning Ridge, New South Wales, Australia
Proprietary mine, Broken Hill, New South Wales, Australia
Prospect Hill, New South Wales, Australia
Warranulla, New South wales, Australia
White Cliffs, New South Wales, Australia
Mina Flores mine, Huanuni district, Oruro Dept., Bolivia
Uncía, Bustillo, Potosí Dept, Bolivia
Corrego do Urucum pegmatite, Minas Gerais, Brazil
Demix-Varennes quarry, Saint-Amable sill, Varennes, Verchéres Co., Québec, Canada
Mt St.-Hilaire, Rouville Co., Québec, Canada
Poudrette quarry, Mt St.-Hilaire, Rouville Co., Québec, Canada
Bohouskovice, Jihomoravsky, Czech Republic
Botallack mine, Botallack, St. Just, Cornwall, England
Carclase China Clay pit, St. Austell, Cornwall, England
Goonhilly Downs, The Lizard, Cornwall, England
Gunheath China Clay Pit, Stenalees, St.Austell, Cornwall, England
Gunheath pit, Bugle, Hensbarrow Moor, Cornwall, England
Kentmere, Kentmere, Cumbria, England
Rock China Clay pit, St. Austell, Cornwall, England
Rosewarne mine, Gwinear, Cornwall, England
Slip China-stone quarry, St. Dennis, Cornwall, England
Stenna Gwyn Mine, St. Austell, Cornwall, England
Stennagwyn mine, St. Stephen-in-Brannel, Cornwall, England
West Carclaze Pit, St.Austell, Cornwall, England
Wheal Buller, Redruth, Illogan, Cornwall, England
Wheal Carne, St. Just, Cornwall, England
Wheal Damsel, Gwennap, Cornwall, England
Wheal Gorland, Gwennap, Cornwall, England
Wheal Maudlin, Lanlivery, Cornwall, England
Wheal Owles, St. Just, Cornwall, England
Chessy-les-Mines, Rhône, Rhône-Alpes, France
Daniel mine, Schneeberg, Sachsen, Germany
Glücksrad mine, Clausthal-Zellerfeld, Harz Mts, Sachsen, Germany
St. Andreasberg, Hartz Mts, Niedersachsen, Germany
Baveno, Lago Maggiore, Piedmont, Italy
Molinello mine, Val Graveglia, Liguria, Italy
Mount Vesuvius, Naples, Campania, Italy
Val Graveglia, Liguria, Italy
Cerro de Mercado, Durango, Mexico
La Esperanza mine, Durango, Mexico
Erongo Mts, Namibia
Zabkowice Slaskie, Walbrzych, Poland
Aldan Shield, Yakutiya, Siberia, Russia
Dal'negorsk, Primorskiy Kray, Russia
Mutnovskoe, Kamchatka, Russia
Polar Urals, Tyumen Oblast, Russia
Rodnikovoe, Kamchatka, Russia
Talisker Bay, Isle of Skye, Scotland
Pezinok Mine, Malé Karpaty Mts, Slovakia
Hotazel mine, Kalahari, Cape Province, South Africa
Aggregate Industries quarry, Ashland, Middlesex Co., Massachusetts, USA
American mine, Bingham Canyon, Salt Lake Co., Utah, USA
Atlantic City iron mine, Fremont Co., Wyoming, USA
Bound Brook Quarry, Bridgewater, Somerset Co., New Jersey, USA
Case Beryl prospects, Portland, Middlesex Co., Connecticut, USA
Caverns of Sonora, Edwards Plateau, Sutton Co., Texas, USA
Conklin Limestone Quarry, Lincoln, Providence, Rhode Island, USA
Conklin quarry, Lincoln, Providence Co., Rhode Island, USA
Corundum Hill Area, Franklin (Mason Mountain), Macon Co., North Carolina, USA
Crawford & Jackford, Crawford Co., Arkansas, USA
Crestmore Quarry, Crestmore, Riverside Co., California, USA
Diamond Hill Granite quarry, Cumberland, Providence Co., Rhode Island, USA
Dunton Quarry etc, Newry Township, Oxford Co., Maine, USA
Etta Mine (Harney Peak & Pearless), Black Hills, Pennington Co., South Dakota, USA
Fat Jack mine, Lane Mt., Yavapai Co., Arizona, USA
Golconda, Humbolt Co., Nevada, USA
Great Notch Quarry, Little Falls, Passaic Co., New Jersey, USA
Harris Quarry, Lincoln, Providence Co., Rhode Island, USA
Hunting Hill quarry, Rockville, Montgomery Co., Maryland, USA
Italian Mt. Area, Aspen, Gunnison Co., Colorado, USA
Jensen Quarry, Riverside Co., California, USA
King Turquoise mine, Conejos Co., Colorado, USA
Laurel Hill (Snake Hill), Secaucus/Bergen Hill Area, Hudson Co., New Jersey, USA
Lovejoy Gravel pits, Albany, Carroll Co., New Hampshire, USA
Magnet Cove, Hot Spring Co., Arkansas, USA
McCormick (Ide Ledge) quarry, East Providence, Providence Co., Rhode Island, USA
Midas, Elko Co., Nevada, USA
Millington quarry, Millington, Somerset Co., New Jersey, USA
Mineral Mts. Area, Milford, Beaver Co., Utah, USA
Montclair Quarry, Montclair, Passaic Co., New Jersey, USA
New Cornelia Mine, Ajo, Pima Co., Arizona, USA
Old Guard Mine, Tombstone, Cochise Co., Arizona, USA
Opal Butte, Morrow Co., Oregon, USA
Overlook Quarry, Day, Saratoga Co., New York, USA
Rockville, Montgomery Co., Maryland, USA
San Rafael swell/Temple Rock, Green River, Emery Co., Utah, USA
Sedalia Copper Mine, Sedalia, Chaffee Co., Colorado, USA
Sneech Pond Copper mine, Cumberland, Providence Co., Rhode Island, USA
Starrett mines, Warren, Knox Co., Maine, USA
Steamboat Springs, Washoe Co., Nevada, USA
The Geysers, Sonoma Co., California, USA
Thomas Range, Juab Co., Utah, USA
Tombstone, Cochise Co., Arizona, USA
Topaz cove, Thomas Range, Juab Co., Utah, USA
Wah Wah Mountain range, Utah, USA
Watchung Mountain Quarries, Mountainside, Union Co., New Jersey, USA
Windslow, Navajo Co., Arizona, USA
Sima Aonda Superior, Auyán-tepuy, Bolivar, Venezuela

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