Barytocalcite is an anhydrous barium

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

carbonate mineral Carbonate minerals are those minerals containing the carbonate ion, . Carbonate divisions Anhydrous carbonates *Calcite group: trigonal ** Calcite CaCO3 ** Gaspéite (Ni,Mg,Fe2+)CO3 ** Magnesite MgCO3 ** Otavite CdCO3 **Rhodochrosite MnCO3 ** ...

with the chemical formula Ba Ca( C O₃)₂. It is trimorphous with

alstonite Alstonite, also known as bromlite, is a low temperature hydrothermal mineral that is a rare double carbonate of calcium and barium with the formula , sometimes with some strontium. Barytocalcite and paralstonite have the same formula but different ...

and paralstonite, that is to say the three minerals have the same formula but different structures. Baryte and

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

pseudomorphs after barytocalcite have been observed. Barytocalcite crystallizes in the

monoclinic crystal system In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic ...

, typically as massive to druzy accumulations of transparent white to yellow to grey aggregates of slender prismatic crystals. It has a

Mohs hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by t ...

of 4 and a

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 3.64 to 3.71. It was first described in 1824 for an occurrence in the Blagill Mine in

North Pennines The North Pennines is the northernmost section of the Pennine range of hills which runs north–south through northern England. It lies between Carlisle to the west and Darlington to the east. It is bounded to the north by the Tyne Valley and ...

Cumbria Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. C ...

( Cumberland),

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

, and named for its composition.

Structure

The mineral crystallises in the

. Most sources put it in the prismatic class 2/m, 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 uncha ...

P2₁/m, but Webmin puts it in the

sphenoidal The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the or ...

class 2 with space group P2₁. The structure is similar to that of dolomite, but with two crystallographically different CO₃ groups. The cation layers are stacked in an ABCABC... stacking pattern, repeating every 3 layers. The Ca

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

is coordinated to 7 oxygens.

Unit cell

All sources give

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 ...

parameters whose values rounded down are a = 8.1 Å, b = 5.2 Å, c = 6.5 Å and β = 106°, with two formula units per unit cell (Z = 2). The primary source has a = 8.092 Å, b = 5.2344 Å, c = 6.544 Å, β = 106.05° and Z=2.

Appearance

Barytocalcite often forms oriented growths on baryte, and calcite,

witherite Witherite is a barium carbonate mineral, Ba C O3, in the aragonite group. Witherite crystallizes in the orthorhombic system and virtually always is twinned. The mineral is colorless, milky-white, grey, pale-yellow, green, to pale-brown. The spec ...

and baryte can be

epitaxial Epitaxy refers to a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epit ...

on barytocalcite. Crystals are normally short to long prismatic and striated. They are transparent to translucent, colourless, white, greyish, greenish or yellowish with a white streak and a vitreous to resinous lustre.

Optical properties

Barytocalcite is a biaxial (-) mineral with

refractive indices In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

n_α = 1.525, n_β = 1.684 and n_γ = 1.686. The maximum birefringence (the difference in refractive index between light travelling through the crystal with different polarizations) is δ = 0.161. The optic angle 2V is the angle between the two optic axes in a

biaxial In crystal optics, the index ellipsoid (also known as the ''optical indicatrix'' or sometimes as the ''dielectric ellipsoid'') is a geometric construction which concisely represents the refractive index, refractive indices and as ...

crystal. The measured values of 2V for this mineral is 15°. It is also possible to calculate a theoretical value of 2V from the measured values of the

. The calculated value for barytocalcite is 10°. 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 barytocalcite 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 barytocalcite Z is parallel to the b axis, X is at an angle of 64° to the c axis and Y is at an angle of 26° to the c axis. Sources disagree about

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

. Webmin describes the mineral as non-fluorescent, Dana categorises it as weakly fluorescent and Mindat states that it is fluorescent dull yellow under both longwave and shortwave

ultraviolet light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

Physical properties

Barytocalcite has at least one perfect and one imperfect cleavage. It is a brittle mineral, and breaks with an uneven to conchoidal fracture. It is quite soft, with a

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 ...

4, the same as that of

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs sca ...

. Calcite CaCO₃ and dolomite CaMg(CO₃)₂ are

carbonates A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

where

Ca and

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

Mg replace the barium in the formula for barytocalcite, BaCa(CO₃)₂. These two minerals are even softer than barytocalcite, and much less dense. Barytocalcite has

3.7. This is higher than that of calcite (2.7) or dolomite (2.85) because the barium atom is very heavy, with

atomic mass The atomic mass (''m''a or ''m'') is the mass of an atom. Although the SI unit of mass is the kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (symbol: Da) – equivalently, unified atomic mass unit (u). 1&nb ...

137, which is much more than magnesium at 24 and calcium at 40. Barytocalcite is soluble in dilute

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

HCl and it is not

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...

Type locality

The type locality is the Blagill Mine, Nent Valley,

Alston Moor Alston Moor, formerly known as Alston with Garrigill, is a civil parish and electoral ward in Cumbria, England, based around the small town of Alston. It is set in the moorlands of the North Pennines, mostly at an altitude of over 1000 feet. T ...

District, North Pennines, North and Western Region, Cumbria, England. This mine is no longer operative, and it has been designated a site of Site of Special Scientific Interest so collecting is no longer allowed. In the past lustrous, transparent, prismatic crystals of barytocalcite have been found thereMineralogical Record (2010) supplement to 41-1:60 (2010) in veins in

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

, associated with

, calcite and baryte.

Other localities

* Canada: Brunswick No 12 Mine, near Bathurst, Gloucester County, New Brunswick. Associated with edingtoniteTschernich (1992) Zeolites of the World. Geoscience Press * England: Nentsberry Haggs Mine,

, Cumbria. A 21 cm specimen with lustrous honey-coloured crystals of barytocalcite to 2 cm on crystalline

was collected here in 1972, and well formed crystals of barytocalcite were found in the 1990s * England: Fallowfield Mine, near Hexham, Northumberland – minor amounts of barytocalcite have been found here * Russia: Found in baryte ore of the Tolecheinsli deposit,

Krasnoyarsk Krasnoyarsk ( ; rus, Красноя́рск, a=Ru-Красноярск2.ogg, p=krəsnɐˈjarsk) (in semantic translation - Red Ravine City) is the largest city and administrative center of Krasnoyarsk Krai, Russia. It is situated along the Yeni ...

region, Siberia, Russia * Sweden: Found with hedyphane and

hausmannite Hausmannite is a complex oxide of manganese containing both di- and tri-valent manganese. The formula can be represented as Mn2+Mn3+2O4. It belongs to the spinel group and forms tetragonal crystals. Hausmannite is a brown to black metallic minera ...

at Langban, Varmland, Sweden * US: Hutter Mine (Herter Magnetite Mine), James River-Roanoke River Mn-Fe-Ba District,

Pittsylvania County, Virginia Pittsylvania County is a county located in the Commonwealth of Virginia. As of the 2020 United States Census, the population was 60,501. Chatham is the county seat. Pittsylvania County is included in the Danville, VA Micropolitan Statistical A ...

. Barytocalcite occurs here and is probably the source of barium for the formation of the rare mica kinoshitaliteTracy and Beard (2003) American Mineralogist 88:740 to 747 * US: South Ouray,

Uintah County, Utah Uintah County ( ) is a county in the U.S. state of Utah. As of the 2020 United States Census the population was 35,620. Its county seat and largest city is Vernal. The county was named for the portion of the Ute Indian tribe that lived in th ...

. Barytocalcite occurs in the dolomitic

oil shale Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitut ...

of the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

Green River formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine ...

of South OurayChao, Evans, Skinner and Milton (1961) American Mineralogist 46:379

References

{{commons Barium minerals Calcium minerals Carbonate minerals Monoclinic minerals Minerals in space group 11 Luminescent minerals