Carlosruizite is a

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

selenate The selenate ion is . Selenates are analogous to sulfates and have similar chemistry. They are highly soluble in aqueous solutions at ambient temperatures. Unlike sulfate, selenate is a somewhat good oxidizer; it can be reduced to selenite o ...

–

iodate An iodate is the polyatomic anion with the formula . It is the most common form of iodine in nature, as it comprises the major iodine-containing ores. Iodate salts are often colorless. They are the salts of iodic acid. Structure Iodate is pyr ...

mineral with chemical formula: K₆( Na,K)₄Na₆ Mg₁₀( Se O₄)₁₂( IO₃)₁₂·12 H₂O. It has a low density (

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest ...

of 3.36), colorless to pale yellow, transparent mineral which crystallizes in the

trigonal In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crystal ...

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 poin ...

.Webmineral.com
/ref> It forms a series with fuenzalidaite. It was first discovered in 1994 in the locality of Zapiga,

Tarapacá Region The Tarapacá Region ( es, Región de Tarapacá, ) is one of Chile's 16 first-order administrative divisions. It comprises two provinces, Iquique and Tamarugal. It borders the Chilean Arica and Parinacota Region to the north, Bolivia's Orur ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

. Its name came from Carlos Ruiz Fuller (1916–1997), founder of the Institute of Geological Investigations.Mindat.org
/ref> It is found in samples of iquiqueite leached from caliche amarillo (yellow nitrate ore).

Composition

Carlosruizite and fuenzalidaite are members of a solid solution series K₆(Na,K)₄Na₆Mg₁₀(XO₄)₁₂(IO₃)₁₂·12H₂O, for which the end-members have X = Se for the former and X = S for the latter. With the exception of selenium, the components of these minerals are widespread constituents of the Chilean nitrate

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...

s. Se was not known to occur in these ores until it was discovered as a major component in carlosruizite by

X-ray spectroscopy X-ray spectroscopy is a general term for several spectroscopic techniques for characterization of materials by using x-ray radiation. Characteristic X-ray spectroscopy When an electron from the inner shell of an atom is excited by the energy o ...

in the scanning electron microscope (SEM). Subsequent analyses of several specimens of nitrate ore from scattered localities in the

an nitrate fields showed them all to contain Se in amounts ranging from a few

parts per million In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, th ...

to nearly 50 ppm.Konnert J.A., Evans H.T., McGee J.J., and Ericksen G.E. (1994) Mineralogical studies of the nitrate deposits of Chile: VII. Two new saline minerals with the composition K₆(Na,K)₄Na ₆Mg₁₀(XO₄)₁₂(IO₃)₁₂·12H₂O: Fuenzalidaite (X = S) and carlosruizite (X = Se). American Mineralogist, 79, 1003-1008.

Geologic occurrence

Small amounts (a few tens of milligrams each) of carlosruizite were first found in nitrate ore from two localities in the Chilean nitrate fields. Carlosruizite was found as ~200 μm platy crystals in samples of iquiqueite, Na₄K₃Mg(CrO₄)B₂₄O₃₉(OH)·12H₂O,Ericksen, G.E., Mrose, M.E., Marinenko, J.W., and McGee, J.J. (1986) Mineralogical studies of the nitrate deposits of Chile. V. Iquiqueite, Na₄K₃Mg(CrO₄)B₂₄O₃₉(OH)·12H₂O, a new saline mineral. American Mineralogist, 71, 830-836. obtained by

leaching Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent). and may refer to: * Leaching (agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amou ...

''caliche amarillo'' (yellow nitrate ore) from samples in the

Iquique Iquique () is a port city and commune in northern Chile, capital of both the Iquique Province and Tarapacá Region. It lies on the Pacific coast, west of the Pampa del Tamarugal, which is part of the Atacama Desert. It has a population of 191, ...

office of the former Servicio de Minas del Estado of Chile, now the

National Geology and Mining Service 250px, Sernageomin building in Providencia, Santiago. The National Geology and Mining Service ( es, Servicio Nacional de Geología y Minería; SERNAGEOMIN) is a Chilean government agency. Its function is to provide geological information and adv ...

(SERNAGEOMIN). The field locality of these samples is not precisely known but probably lies in the vicinity of Zapiga, where ''caliche amarillo'' is especially abundant. Of the 25 species of saline minerals that have been identified in the Chilean nitrate ores, 11 are known to be associated with carlosruizite.Ericksen, G.E. (1993) Upper Tertiary and Quaternary continental saline deposits in the central Andes. In R.V. Kirkham, W.D. Sinclair, R.I. Thorpe, and J.M. Duke, Eds., Mineral deposit modelling, in press. Geological Association of Canada, Ottawa. The dense ''caliche amarillo'' containing carlosruizite consists chiefly of a fine-grained mixture of

nitratine Nitratine or nitratite, also known as cubic niter (UK: nitre), soda niter or Chile saltpeter (UK: Chile saltpetre), is a mineral, the naturally occurring form of sodium nitrate, NaNO3. Chemically it is the sodium analogue of saltpeter. Nitratine ...

halite Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...

, and darapskite. The residues of leaching this material in cold water contain dietzeite a₂(IO₃)₂(CrO₄) briiggenire a(IO₃)₂·H₂O tarapacaite (K₂CrO₄), lopezite (K₂Cr₂O₇),

ulexite Ulexite (NaCaB5O6(OH)6·5H2O, hydrated sodium calcium borate hydroxide), sometimes known as TV rock or Television stone, is a mineral occurring in silky white rounded crystalline masses or in parallel fibers. The natural fibers of ulexite conduc ...

aCaB₅0₆(OH)₆·5H₂O probertite aCaB₅O₇(OH)₄·3H₂O and

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 drywal ...

(CaSO₄·2H₂O).

Atomic structure

Carlosruizite is a trigonal mineral with

lattice spacing A lattice constant or lattice parameter is one of the physical dimensions and angles that determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal. A simple cubic crystal has ...

a=9.59, c=27.56 Å, Z=1 and V=2,195.11. It has a structure bearing a distant resemblance to those of the alunite group. These structures are rhombohedral or trigonal, with axial lengths of about 7 Å, and contain layers consisting of sheets of tetrahedral sulfate anions joined to an ^{/sup>Al (or ^{/sup>Fe) sheet, including OH groups, and the layers are separated
by K (or Na) ions. Carlosruizite was, along with fuenzalidaite, the first minerals of this type in which a layer of IO₃ groups occurred.

Physical properties

Carlosruizite occurs as thin, colorless to pale yellow, transparent, euhedral

Euhedral crystals (also known as idiomorphic or automorphic crystals) are those that are well-formed, with sharp, easily recognised faces. The opposite is anhedral (also known as '' xenomorphic'' or ''allotriomorphic''): a rock with an anhedra ...
, platy crystals with hexagonal outline, generally <200 μm in diameter and 20 μm thick. The crystals have a pseudorhombohedral 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.
, flattened on with beveled edges . They are slowly soluble in H₂O. Surfaces of some crystals show abundant round or elongate cavities, which probably were formerly filled with saline fluids. The crystals are brittle

A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Br ...
and break easily into multiple fragments. Hardness

In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
is on the order of 2-3. The luster is vitreous.

Discovery and naming

George E. Ericksen discovered and named carlosruizite in 1994. It was named to honor the Chilean geologist and mining engineer Carlos Ruiz Fuller, who played a major role in the 20th century development of geology in Chile, by planning and directing the first national geological institution (inaugurated in 1957), the Instituto de Investigaciones Geológicas, now the Servicio Nacional de Geología y Minería, which began the first systematic geologic mapping and study of mineral deposits in Chile.

References

{{Reflist

Potassium minerals
Sodium minerals
Magnesium minerals
Chromium minerals
Selenium minerals
Trigonal minerals
Minerals in space group 165}}