Roscoelite
Encyclopedia
Roscoelite is a green mineral from the mica
group that contains vanadium
.
The chemical formula is K
(V
3+, Al, Mg
)2AlSi
3O
10(OH
)2.
Crystals of roscoelite take on the monoclinic form, and are from the 2/m point group
.
The appearance is semi transparent to translucent coloured olive brown to green brown. The luster
is pearly. The mineral shows pleochroism
with X showing green-brown, and Y and Z axes showing olive-green colour. The mineral was named after Henry Enfield Roscoe
who first produced vanadium metal.
with aluminium
substituted with vanadium. Vanadium can also be substituted by magnesium
, iron
, or manganese
.
with an angle between axes of β=101.0°. The tetrahedral cation-oxygen atom distance is 164.1 pm, The distance from the cation to the oxygen in the octahedral plan is 202 pm.
-silver
-tellurium low temperature epithermal deposits where it occurs along with quartz
, fluorite
, pyrite
and carbonate
s, or oxidized low temperature uranium
-vanadium
ore
s in sedimentary rock
s, where it occurs with corvusite, hewettite, carnotite
and tyuyamunite. Roecoelite is considered a gangue
mineral of no value when found with gold. However it has also been used as a vanadium ore.
In the Mt. Kare mine in New Guinea the mineral occurs with gold and is an important maker of gold deposits. The temperature of the geothermal fluid that depositied the roscoelite was from 127 to 167 °C. The fluid contained a high level of salt
and also contained carbon dioxide
, methane
, carbonyl sulfide
and other minor amounts of rock forming elements.
, it was the principal vanadium
ore mineral at the mines at Placerville, Colorado
. In Australia roscoelite has been found at Kalgoorlie, Radium Hill
and the Kintore Open Cut at Broken Hill.
Mica
The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...
group that contains vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
.
The chemical formula is K
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
(V
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
3+, Al, Mg
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
)2AlSi
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
3O
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
10(OH
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
)2.
Crystals of roscoelite take on the monoclinic form, and are from the 2/m point group
Point group
In geometry, a point group is a group of geometric symmetries that keep at least one point fixed. Point groups can exist in a Euclidean space with any dimension, and every point group in dimension d is a subgroup of the orthogonal group O...
.
The appearance is semi transparent to translucent coloured olive brown to green brown. The luster
Lustre (mineralogy)
Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....
is pearly. The mineral shows pleochroism
Pleochroism
Pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles with polarized light.- Background :Anisotropic crystals will have optical properties that vary with the direction of light...
with X showing green-brown, and Y and Z axes showing olive-green colour. The mineral was named after Henry Enfield Roscoe
Henry Enfield Roscoe
Sir Henry Enfield Roscoe, FRS was an English chemist. He is particularly noted for early work on vanadium and for photochemical studies.- Life and work :...
who first produced vanadium metal.
Chemical properties
Roscoelite is a muscoviteMuscovite
Muscovite is a phyllosilicate mineral of aluminium and potassium with formula KAl22, or 236. It has a highly-perfect basal cleavage yielding remarkably-thin laminæ which are often highly elastic...
with aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
substituted with vanadium. Vanadium can also be substituted by magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, or manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
.
Physical properties
It is soft and the density is 2.93±0.01. The unit cell has dimensions- a = 526 pmPicometreA picometre is a unit of length in the metric system, equal to one trillionth, i.e. of a metre, which is the current SI base unit of length...
- b = 909 pm
- c = 1025 pm,
with an angle between axes of β=101.0°. The tetrahedral cation-oxygen atom distance is 164.1 pm, The distance from the cation to the oxygen in the octahedral plan is 202 pm.
Formation
Two kinds of mineral deposits contain roscoelite, either goldGold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
-silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
-tellurium low temperature epithermal deposits where it occurs along with quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
, pyrite
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
and carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
s, or oxidized low temperature uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
-vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
s in sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
s, where it occurs with corvusite, hewettite, carnotite
Carnotite
Carnotite is a potassium uranium vanadate radioactive mineral with chemical formula: K222·3H2O. The water content can vary and small amounts of calcium, barium, magnesium, iron, and sodium are often present.-Occurrence:...
and tyuyamunite. Roecoelite is considered a gangue
Gangue
In mining, gangue is the commercially worthless material that surrounds, or is closely mixed with, a wanted mineral in an ore deposit. The separation of mineral from gangue is known as mineral processing, mineral dressing or ore dressing and it is a necessary and often significant aspect of mining...
mineral of no value when found with gold. However it has also been used as a vanadium ore.
In the Mt. Kare mine in New Guinea the mineral occurs with gold and is an important maker of gold deposits. The temperature of the geothermal fluid that depositied the roscoelite was from 127 to 167 °C. The fluid contained a high level of salt
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
and also contained carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
, carbonyl sulfide
Carbonyl sulfide
Carbonyl sulfide is the chemical compound with the formula OCS. Commonly written as COS, it is a colourless flammable gas with an unpleasant odor. It is a linear molecule consisting of a carbonyl group double bonded to a sulfur atom...
and other minor amounts of rock forming elements.
Occurrence
The mineral has been found in numerous places in USA, Australia, Japan, Gabon, Fiji, New Guineaand Czech Republic. In the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, it was the principal vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
ore mineral at the mines at Placerville, Colorado
Placerville, Colorado
Placerville is an unincorporated town and a U.S. Post Office located in San Miguel County, Colorado, United States. The Placerville Post Office has the ZIP Code 81430.-History:...
. In Australia roscoelite has been found at Kalgoorlie, Radium Hill
Radium Hill
Radium Hill is a former minesite in South Australia which operated from 1906 until 1961. It was Australia's first uranium mine, years before the country's next major mines at Rum Jungle in the Northern Territory , and the Mary Kathleen mine in Queensland...
and the Kintore Open Cut at Broken Hill.