Huemulite is a mineral with formula Na
4Mg(V
10O
28)·24H
2O that is yellow to orange in color. It was first discovered in
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
in 1959 and described in 1966. The mineral is named for the Huemul mine in which it was discovered.
Occurrence and properties
Huemulite is yellowish orange to orange and bright in color.
[ The mineral occurs as thin films, aggregates of fine fibers, ]botryoidal
A botryoidal ( ) texture or mineral habit, is one in which the mineral has an external form composed of many rounded segments, named for the Ancient Greek (), meaning "a bunch of grapes".Adjective form: ''botruoeidēs'' This is a common form fo ...
masses, and interstitial
An interstitial space or interstice is a space between structures or objects.
In particular, interstitial may refer to:
Biology
* Interstitial cell tumor
* Interstitial cell, any cell that lies between other cells
* Interstitial collagenase, ...
filling in host sandstone.[ Huemulite has been found in Argentina, the Czech Republic, the United Kingdom, and the United States.][ It occurs in association with ]epsomite
Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula MgSO4·7H2O.
Epsomite crystallizes in the orthorhombic system as rarely found acicular or fibrous crystals, the normal form is as massi ...
, gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...
, hummerite, rossite, and thenardite.
Huemulite is a member of the pascoite group.[ It melts at to become a red liquid. Huemulite dissolves readily in cold water to produce an orange-yellow ]solution
Solution may refer to:
* Solution (chemistry), a mixture where one substance is dissolved in another
* Solution (equation), in mathematics
** Numerical solution, in numerical analysis, approximate solutions within specified error bounds
* Soluti ...
with a pH of 5.5 to 6.5.[Gordillo, p. 12.]
Formation and synthesis
In Argentina, the mineral formed after mine tunnels were cut through Cu- U deposits in sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
and conglomerate.[Gordillo, p. 3.] The vanadium in huemulite is thought to originate from asphaltic material that occurs in association with the sandstone.[
Huemulite can be synthesized by mixing ]stoichiometric
Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions.
Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equal ...
proportions of vanadium pentoxide
Vanadium(V) oxide (''vanadia'') is the inorganic compound with the formula V2 O5. Commonly known as vanadium pentoxide, it is a brown/yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because o ...
, magnesium carbonate
Magnesium carbonate, (archaic name magnesia alba), is an inorganic salt that is a colourless or white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals.
Forms
The most common magnesium carbonate forms are ...
, and sodium carbonate
Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions ...
in cold water in a humid environment. The mixture is heated to dissolve the compounds which react with each other as CO2 is drawn off. The solution is then concentrated, excess vanadic acid is removed by filtration, and allowed to cool and crystallize.[
Since huemulite dissolves easily in water, it can be recrystallized by evaporating the mineral solution.][ When evaporated slowly, the process creates well-formed crystals up to and . In a more humid environment, fibrous crystals or acicular radial aggregates are formed.][
Both recrystallized and synthetic huemulite have tabular ]habit
A habit (or wont as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously. .[
]
Structure
Huemulite exhibits the triclinic
180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ )
In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal is ...
crystal system
In crystallography, a crystal system is a set of point groups (a group of geometric symmetries with at least one fixed point). A lattice system is a set of Bravais lattices. Space groups are classified into crystal systems according to their po ...
with space group
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unchan ...
P and one formula unit
In chemistry, a formula unit is the empirical formula of any ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound. Exa ...
per unit cell
In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector, for example) does not necessaril ...
.[ The ]crystal structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...
consists of decavanadate anions (V10O28)6− linked by an interstitial complex of isolated 2O)6">g(H2O)6sup>2+ and an infinite zigzag chain of 4(H2O)14">a4(H2O)14sup>4+. There are a further four isolated H2O groups, two of which are positionally disordered.[Colombo, p. 849.]
History
Huemulite was discovered in the area of Malargüe
Malargüe () is a city in the southwest part of province of Mendoza, Argentina, about 370 km south of the provincial capital Mendoza. It is the head town of the Malargüe Department, and it has about 27,000 inhabitants as per the .
Overvie ...
in Mendoza Province
Mendoza, officially Province of Mendoza, is a province of Argentina, in the western central part of the country in the Cuyo region. It borders San Juan to the north, La Pampa and Neuquén to the south, San Luis to the east, and the republic o ...
, Argentina.[ The first specimen was collected in 1959 by V. Angelelli of the Geology Department of ]CNEA
The National Atomic Energy Commission ( es, Comisión Nacional de Energía Atómica, CNEA) is the Argentine government agency in charge of nuclear energy research and development.
The agency was created on May 31, 1950, with the mission of deve ...
on level -18 of the Agua Botada ore body. The specimen was sent to E. Linares who determined it to be unlike any known mineral.[Gordillo, p. 2.] Further specimens were collected in the mine as well as the nearby Huemul and Agua Botada Sur mines.[Gordillo, pp. 2–3.] In 1963, a preliminary report on the mineral was presented to the II Argentine Geological Congress. In 1964, the unit cell
In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector, for example) does not necessaril ...
was measured at Yale University
Yale University is a private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and among the most prestigious in the wo ...
by Linares and H. Winchell and the mineral's chemical and physical properties were checked by C. E. Gordillo and R. O. Toubes.[ The mineral was named ''huemulite'' after the Huemul mine in which it was discovered. On May 19, 1965, the mineral and name were approved by the Commission on New Minerals and Mineral Names of the IMA. Huemulite was described in 1966 in the journal ''American Mineralogist'' by Gordillo, Linares, Toubes, and Winchell.][Gordillo, p. 1.]
Synthetic huemulite was deposited by Gordillo in the Museo de Mineralogía of the Universidad Nacional de Córdoba
Universidad (Spanish for "university") may refer to:
Places
* Universidad, San Juan, Puerto Rico
* Universidad (Madrid)
Football clubs
* Universidad SC, a Guatemalan football club that represents the Universidad de San Carlos de Guatemala
...
.[Colombo, p. 850.] No type specimens
In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes t ...
were designated by them, however, a type specimen was donated by Linares to the National Museum of Natural History
The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7 ...
in Washington, D.C. Unfortunately, during a 2011 study, the only mineral detected similar to huemulite was lasalite.[Colombo, p. 855.] It was determined that Gordillo ''et al.'' most likely used fully hydrated huemulite in chemical analysis and partially dehydrated huemulite in determining the mineral's powder X-ray diffraction
Powder diffraction is a scientific technique using X-ray, neutron, or electron diffraction on powder or microcrystalline samples for structural characterization of materials. An instrument dedicated to performing such powder measurements is cal ...
.[Colombo, p. 857.]
Analysis
Huemulite in its natural form is too fine-grained for accurate study of its physical and optical properties;[Gordillo, pp. 4–5.] however, it can readily be recrystallized after dissolving the mineral in water. As far as can be determined, both recrystallized and synthetic huemulite are identical to natural specimens.[Gordillo, p. 5.]
References
;Bibliography
*
*{{cite journal, last1=Gordillo, first1=C. E., last2=Linares, first2=E., last3=Toubes, first3=R. O., last4=Winchell, first4=H., title=Huemulite, Na4MgV10O28·24H2O, a new hydrous sodium and magnesium vanadate from Huemul Mine, Mendoza Province, Argentina, journal=American Mineralogist, date=January–February 1966, volume=51, issue=1 & 2, pages=1–13, url=http://www.minsocam.org/ammin/AM51/AM51_1.pdf
External links
Photos of huemulite
from mindat.org
Triclinic minerals
Sodium minerals
Magnesium minerals
Vanadate minerals
Hydrates
Minerals in space group 2