# Geominerals/Carbonates

Carbonates have more than 25 molecular % carbonate (CO $_3$).

## Abenakiite-(Ce)

Abenakiite-(Ce) has the chemical formula Na $_{26}$Ce $_6$(SiO $_3$) $_6$(PO $_4$) $_6$(CO $_3$) $_6$(S$^{4+}$ O $_2$)O. Abenakiite-(Ce) (IMA1991-054; IMA Symbol Abk-Ce) is a mineral of sodium, cerium, neodymium, lanthanum, praseodymium, thorium, samarium, oxygen, sulfur, carbon, phosphorus, and silicon. The silicate groups may be given as the cyclic Si $_6$O $_{18}$ grouping. Its Mohs scale rating is 4 to 5.
Abenakiite-(Ce) was discovered in a sodalite syenite xenolith at Mont Saint-Hilaire, Québec, Canada, together with aegirine, eudialyte, manganoneptunite, polylithionite, serandite, and steenstrupine-(Ce).
Combination of elements in abenakiite-(Ce) is unique. Somewhat chemically similar mineral is steenstrupine-(Ce). The hyper-sodium abenakiite-(Ce) is also unique in supposed presence of sulfur dioxide ligand. With a single grain (originally) found, abenakiite-(Ce) is extremely rare.
In the crystal structure, described as a hexagonal net, of abenakiite-(Ce) there are:
* chains of NaO $_7$ polyhedra, connected with PO $_4$ groups
* columns with six-membered rings of NaO $_7$, and NaO $_7$-REEO $_6$, and SiO $_4$ polyhedra (REE - rare earth elements)
* CO $_3$ groups, NaO $_6$ octahedra, and disordered SO $_2$ ligands within the columns

## Adamsites-(Y)

Adamsite-(Y) (previously IMA 1999-020), chemical formula NaY(CO $_3$) $_2$·6H $_2$O is a mineral of sodium, yttrium, carbon, oxygen, and hydrogen, named after Frank Dawson Adams (1859–1942), professor of geology, McGill University, with a Mohs scale rating of 3, IMA symbol is Ads-Y.

## Albrechtschraufites

Albrechtschraufite (International Mineralogical Association (IMA) symbol: Asf) is a very rare complex hydrated calcium and magnesium-bearing uranyl fluoride carbonate mineral with formula Ca $_4$Mg(UO $_2$) $_2$(CO $_3$) $_6$F $_2$·17H $_2$O. Its molar weight is 1,428.98 g, color yellow-green, streak white, density 2.6 g/cm$^3$, Mohs hardness 2-3, and luster is vitreous (glassy). It is named after Albrecht Schrauf (1837–1897), Professor of Mineralogy, University of Vienna. Its type locality is Jáchymov, Jáchymov District, Krušné Hory Mountains, Karlovy Vary Region, Bohemia, Czech Republic.

## Alstonites

Alstonite (International Mineralogical Association (IMA) symbol: Asn), also known as bromlite, is a low temperature hydrothermal mineral that is a rare double carbonate of calcium and barium with the formula BaCa(CO $_3$) $_2$, sometimes with some strontium. Barytocalcite and paralstonite have the same formula but different structures, so these three minerals are said to be trimorphous. Alstonite is triclinic but barytocalcite is monoclinic and paralstonite is trigonal. The species was named Bromlite by Thomas Thomson in 1837 after the Bromley-Hill mine. This mine was owned by Thomas Shaw and business partner Jacob Walton between 1816 and 1874. The owners then Subcontracted to groups of independent miners, basing their pay on the amount of drifting accomplished, the amount of ore produced, or a combination of the two. This system worked well, and the Brownley Hill mine became one of the more productive mines on Alston Moor during the Middle 1800s. By the early 1870s the seams of lead were being exhausted and in 1874 the lease was then taken over by the Brownley Hill Mining which concentrated on Zinc mining, which failed to make a profit. and alstonite by August Breithaupt of the Freiberg University of Mining and Technology in 1841, after Alston, Cumbria, the base of operations of the mineral dealer from whom the first samples were obtained by Thomson in 1834. Both of these names have been in common use.
Alstonite is triclinic, but appears pseudo-orthorhombic crystal because of twinning. The space group is P1 or P1. Alstonite appears to have a superstructure based on paralstonite without long range order of the metal cations or the CO $_3$ groups. The structure of paralstonite is similar to that of other double carbonates.
The number of formula units, Z, in the triclinic unit cell is given as 10 or 12, and the unit cell parameters are a = 17.38 Å, b = 14.40 Å, c = 6.123 Å, α = 90.35°, β = 90.12°, γ = 120.08°. The Handbook of Mineralogy, however, describes the mineral in terms of a pseudo-orthorhombic unit cell, with space group C1 or C1, Z = 24, and unit cell parameters a = 30.14 Å, b = 17.40 Å, c = 6.12 Å, α = β = γ = 90°.
Simple crystals of alstonite are not known. The crystals are invariably complex twins formed by repeated twinning, and have the form of doubly terminated pseudo-hexagonal pyramids, like those of witherite but more acute. The faces are horizontally striated perpendicular to the pseudohexagonal c crystal axis and they are divided vertically by a medial, slightly reentrant twinning line parallel to the pseudohexagonal c axis.
Crystals are colourless to snow white, yellow-gray, pale gray, pale cream, pink, or pale rose-red, but the colour may fade on exposure to light. They are transparent to translucent with a white streak and vitreous lustre. The examination in polarized light of a transverse section shows that each compound crystal is built up of six differently oriented individuals arranged in twelve segments.
Alstonite is a biaxial (-) mineral with refractive indices n$_α$ =1.526, n$_β$ = 1.671, n$_γ$ = 1.672. The maximum birefringence (the difference in refractive index between light travelling through the crystal with different polarizations) is δ = 0.146.
The optic angle 2V is the angle between the two optic axes in a biaxial crystal. The measured values of 2V for this mineral is 6°. It is also possible to calculate a theoretical value of 2V from the measured values of the refractive indices. The calculated value for alstonite is 8°. If the colour of the incident light is changed, then the refractive indices are modified, and the value of 2V changes. This is known as dispersion of the optic axes. For alstonite the effect is weak, with 2V larger for red light than for violet light (r > v).
The optical directions X, Y, and Z are the directions of travel of light with refractive indices n$_α$, n$_β$, and n$_γ$ respectively. In general they are not the same as the directions a, b, and c of the crystallographic axes. For alstonite X, Y, and Z are parallel to the c, a, and b crystal axes respectively.
Alstonite fluoresces weak yellow under shortwave and longwave ultraviolet light.
Twinning in alstonite is ubiquitous, forming pseudohexagonal groups. The mineral has one imperfect cleavage and it breaks with an uneven fracture. It is not very hard, with a Mohs hardness of just 4 to ​4 $^1$⁄$_2$, a little harder than fluorite, and its specific gravity is 3.70. It is soluble in dilute hydrochloric acid (HCl) and it is not radioactive. The trimorphs alstonite, paralstonite, and barytocalcite all have similar physical properties.
There are two type localities, both in the north of England. One is the Bromley Hill Mine (Bloomsberry Horse Level), Nenthead, Alston Moor District, North Pennines, Cumbria, and the other is the Fallowfield Mine, Acomb, Hexham, Tyne Valley, Northumberland. The type material is held at the Freiberg University of Mining and Technology, Germany, 15818.
At the type locality at Brownley Hill, alstonite occurs in low-temperature lead–zinc hydrothermal deposits associated with witherite, calcite, and baryte. The crystals are white to colourless or faintly pink acute pseudohexagonal pyramids or dipyramids up to 6 mm long. In some specimens the alstonite is intergrown with very thin hexagonal platy crystals of nailhead calcite. Alstonite commonly encrusts compact crystalline white to pale pink baryte. Similar crystals have been found at Fallowfield. It occurs typically in low-temperature hydrothermal lead–zinc ore deposits, as is the case at the type localities, and it has also been reported as a rare phase in carbonatites. It occurs associated with calcite, baryte, ankerite, siderite, benstonite, galena, sphalerite, pyrite, and quartz.

## Calcites

Calcite has the chemical formula CaCO $_3$.
Calcite contains one oxide: CO $_3$, or carbonate. It is 50 molecular % carbonate and 20 at % calcium.
The image on the right is a large crystal of Calcite, also known as Icelandic Spar, on display at the National Museum of Natural History in Washington, DC.

## Carrboydites

Carrboydite has the formula: (Ni $_{(1-x)}$Al $_x$)(SO $_4$) $_{(x/2)}$(OH) $_2$·nH $_2$O, where (x < 0.5, n > 3x/2), is a member of the Glaucocerinite Group > Hydrotalcite Supergroup, in the Hexagonal Crystal System, named for the Carr Boyd nickel mine, Australia, the type locality.
Carrboydite has the Chemical Formula: (Ni,Cu) $_{14}$Al $_9$(SO $_4$,CO $_3$)(OH) $_{43}$•7(H $_2$O). The Empirical Formula is Ni $_{10}$Cu $_4$Al $_9$(SO $_4$) $_4$(CO $_3$) $_2$(OH) $_{43}$•7(H $_2$O).
"As part of the recent re-evaluation of the nomenclature of the hydrotalcite supergroup (Mills et al., 2012), carrboydite was identified as a questionable species which needs further investigation."
Environment: "Surface material at a nickel mine."

## Dolomites

Dolomite has the chemical formula: CaMg(CO $_3$) $_2$, which is 10 at % calcium, 10 at % magnesium, 20 at % carbon, 60 at % oxygen and 50 molecular % carbonate.

## Gaspéites

Gaspéite, a very rare nickel carbonate mineral, with the formula (Ni,Fe,Mg)CO $_3$, is named for the place it was first described, in the Gaspé Peninsula, Québec, Canada.
"Gaspe Peninsula, Canada; CO $_2$ by ignition and absorption; after removal of MgO and SiO $_2$ from serpentine, corresponds to (Ni $_{0.49}$Mg $_{0.43}$Fe $_{0.08}$)CO $_3$."
"An uncommon secondary mineral in a Ni-sulfide-bearing vein in metamorphosed siliceous dolostone (Gaspe Peninsula, Canada)".
"Millerite, nickeline, annabergite, gersdorffite, polydymite, heazlewoodite, magnesite, spinel, dolomite (Gaspe Peninsula, Canada); pecoraite, magnesite, siderite, chrysotile, antigorite, magnetite, millerite, polydymite (Otway prospect, Western Australia); glaukosphaerite, mcguinnessite, jamborite (Shinshiro, Japan); liebenbergite, trevorite, nickeloan ludwigite, bunsenite, violarite, millerite, nimite (Bon Accord, South Africa)."
Gaspéite has the chemical formula NiCO $_3$.

## Glaukosphaerites

Glaukosphaerites have the CNMMN/CNMNC approved formula: CuNi(CO $_3$)(OH) $_2$ and the Strunz formula: (Cu,Ni)$_2$[(OH)$_2$|CO$_3$], or (Cu,Ni) $_2$(CO $_3$)(OH) $_2$.
It is a member of the Rosasite Group.
Associated Minerals at Type Locality: Goethite, Quartz, Paratacamite, Gypsum, Magnesite, Malachite, and Clay.

## Hellyerites

Another "non-mixed cationic nickel [carbonate is] hellyerite NiCO$_3$·6H$_2$O$^9$".

## Kambaldaites

Kambaldaites have the formula: NaNi $_4$(CO $_3$) $_3$(OH) $_3$ · 3H $_2$O.
General Appearance of Type Material: Cryptocrystalline veins, layers and concretionary growths up to about 2 mm thick, commonly intergrown with gaspeite, also as encrustations of tiny hexagonal prisms.
Geological Setting of Type Material: Nickel sulfide deposit, as a secondary mineral that has been precipitated on fracture surfaces in oxidizing Ni-Fe sulfide ore.
"The primary sulfides, which occur as assemblages of pentlandite-pyrrhotite-pyrite and pentlandite-millerite-pyrite, have been altered to supergene assemblages consisting largely of violarite and pyrite, which have decomposed on further oxidation to a goethitic residue in which the secondary nickel minerals have been deposited."
"The samples in which the kambaldaite was found are from a depth of about 20 meters, and consist largely of goethite with some reevesite and residual pyrite. The kambaldaite, together with gaspeite and some aragonite, occurs on fracture surfaces in the goethite. The kambaldaite occurs in a variety of types: massive, crystalline, nodular and chalky."

## Magnesites

Occurrence: A primary mineral in igneous or sedimentary rocks; is formed by metamorphism or alteration of serpentine and peridotite; uncommon in marine evaporites and hydrothermal veins; rare in carbonatites.
Geological Setting: Primary mineral is in igneous and sedimentary rocks. Rarely is a gangue mineral in hydrothermal ore veins, and in oceanic salt deposits. Metamorphism is of serpentinites and peridotites.
Polymorphism & Series: Forms two series, with gaspéite and with siderite.
The abundances of certain bonds in certain molecules are sensitive to temperature at which it formed (e.g., abundance of $^{13}$C$^{16}$O$^{18}$O in carbonates as $^{13}$C-$^{18}$O bond). This information has been exploited to form the foundation of clumped isotope geochemistry. Clumped isotope thermometers have been established for carbonate minerals like dolomite, calcite, siderite etc and non-carbonate compounds like methane and oxygen. Depending on the strength of cation-carbonate oxygen (ie, Mg-O, Ca-O) bonds- different carbonate minerals can form or preserve clumped isotopic signatures differently.

## Malachites

Malachite is a mineral that occurs in rocks at or near the interface between Earth's atmosphere and crust.
Malachite is a copper carbonate hydroxide mineral, with the chemical formula Cu $_2$CO $_3$(OH) $_2$, which is 20 at % copper, 10 at % carbon, 20 at % hydrogen, 50 at % oxygen, 20 molecular % carbonate and 40 molecular % hydroxide.
This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fractures and deep, underground spaces, where the water table and hydrothermal fluids provide the means for chemical precipitation. Individual crystals are rare, but occur as slender to acicular prisms. Pseudomorphs after more tabular or blocky azurite crystals also occur.

## Nullaginites

"In nature there exists [the] hydroxy nickel carbonate [mineral] nullaginite Ni $_2$(CO $_3$)(OH) $_2$$^{1-3}$ [...] Nullaginite is monoclinic with point group 2/m and is a member of the rosasite mineral group. Nullaginite is formed in the oxidised zone of nickel rich hydrothermal ore deposits."

## Otwayites

Otwayite has the chemical formula Ni $_2$CO $_3$(OH) $_2$.
Otwayite has the formula: Ni $_2$CO $_3$(OH) $_2$ · H $_2$O.
Geological Setting of Type Material: Narrow veinlets to 1 mm in width, probably late-stage fracture filling, transecting nickeloan serpentine, millerite, polydymite, and apatite.
Otwayite is associated with Widgiemoolthalite.
Occurrence: Otwayite is found in association with nullaginite and hellyerite in the Otway nickel deposit, is found in association with theoprastite, hellyerite, gaspeite and a suite of other nickel carbonate minerals in the Lord Brassey Mine, Tasmania, in association with gaspeite, hellyerite and kambaldaite in the Widgie Townsite nickel gossan, Widgiemooltha, Western Australia, and reported from the Pafuri nickel deposit, South Africa.
It was first described in 1977 from the Otway Nickel Deposit, Nullagine, Pilbara Craton, Western Australia and named for Australian prospector Charles Albert Otway (born 1922).

## Reevesites

Chemical Formula: Ni $_6$Fe$^{3+}$ $_2$(CO $_3$)(OH) $_{16}$•4(H $_2$O).
Environment: Alteration product of a highly weathered iron-nickel meteorite.
Type Locality: Wolf Creek meteorite, found three km west of the Scotia talc mine, Bon Accord area, Barberton, Transvaal, South Africa.
Crystal System: Trigonal.
Member of the Hydrotalcite Group > Hydrotalcite Supergroup.
Geological Setting: Nickel rich ore deposits.
Geological Setting of Type Material: alteration product of a highly weathered iron-nickel meteorite.
Associated Minerals at Type Locality: Goethite, Jarosite, Serpentine Subgroup, Apatite, Lipscombite.

## Smithsonites

Smithsonite has the chemical formula ZnCO $_3$.

## Spurrites

Spurrite is a nesosilicate that can occur naturally as a yellow mineral. Its chemical formula is Ca$_5$(SiO$_4$)$_2$CO$_3$. Spurrite is generally formed in contact metamorphism zones as mafic magmas are intruded into carbonate rocks.

## Takovites

Takovites have the formula: Ni $_6$Al $_2$(OH) $_{16}$(CO $_3$) · 4H $_2$O.
Member of the Hydrotalcite Group > Hydrotalcite Supergroup.
Morphology: Microcrystalline, platy, to 1 µm; commonly in veinlets and massive.

## Zaratites

"In nature there exists [the] hydroxy nickel carbonate [mineral] zaratite Ni$_3$(CO$_3$)(OH)$_4$·4(H$_2$O)$^{4-8}$. [...] Zaratite is of an unknown structure and is an uncommon secondary mineral formed by alteration of chromite, pentlandite, pyrrhotite and millerite in ultramafic rocks."

## Hypotheses

* High-temperature, high-pressure minerals exist in the core of the Earth.
* High-temperature, high-pressure minerals can be produced through natural electrochemistry.