Barytocalcite is an anhydrous

barium Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

calcium Calcium is a chemical element; it has 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 to it ...

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 **Sider ...

with the chemical formula Ba Ca( C O₃)₂. It is trimorphous with alstonite and paralstonite, that is to say the three minerals have the same formula but different structures.

Baryte Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...

and

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

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 sy ...

, typically as massive to druzy accumulations of transparent white to yellow to grey aggregates of slender

prismatic An optical prism is a transparent optics, optical element with flat, polished surfaces that are designed to refraction, refract light. At least one surface must be angled—elements with two parallel surfaces are ''not'' prisms. The most fami ...

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 mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fair ...

of 4 and a

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

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 are the northernmost section of the Pennines, a range of hills which run north–south through northern England. They run along the border between County Durham and Northumberland in the east and Cumbria in the west, and are ...

Cumbria Cumbria ( ) is a ceremonial county in North West England. It borders the Scottish council areas of Dumfries and Galloway and Scottish Borders to the north, Northumberland and County Durham to the east, North Yorkshire to the south-east, Lancash ...

(

Cumberland Cumberland ( ) is an area of North West England which was historically a county. The county was bordered by Northumberland to the north-east, County Durham to the east, Westmorland to the south-east, Lancashire to the south, and the Scottish ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

, and named for its composition.

Structure

The mineral crystallises in the

. Most sources put it in the

class 2/m, with

space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...

P2₁/m, but Webmin puts it in the sphenoidal class 2 with space group P2₁. The structure is similar to that of dolomite, but with two crystallographically different CO₃ groups. The

cation 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 convent ...

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 convent ...

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 In mathematics, a unit vector i ...

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 Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...

, and

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

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 (prefix ''epi-'' means "on top of”) is 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 cry ...

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 the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

n_α = 1.525, n_β = 1.684 and n_γ = 1.686. The maximum

birefringence Birefringence, also called double refraction, is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are described as birefrin ...

(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 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 one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colore ...

. 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 radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of th ...

Physical properties

Barytocalcite has at least one perfect and one imperfect

cleavage Cleavage may refer to: Science * Cleavage (crystal), the way in which a crystal or mineral tends to split * Cleavage (embryo), the division of cells in an early embryo * Cleavage (geology), foliation of rock perpendicular to stress, a result of ...

. It is a brittle mineral, and breaks with an uneven to

conchoidal fracture A conchoidal fracture is a break or fracture of a brittle material that does not follow any natural planes of separation. Mindat.org defines ''conchoidal fracture'' as follows: "a fracture with smooth, curved surfaces, typically slightly concave ...

. It is quite soft, with a

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...

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 scal ...

Calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

CaCO₃ and dolomite CaMg(CO₃)₂ are carbonates where

Ca and

magnesium Magnesium is a chemical element; it has Symbol (chemistry), 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 ...

Mg replace the

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 Atomic mass ( or ) is the mass of a single atom. The atomic mass mostly comes from the combined mass of the protons and neutrons in the nucleus, with minor contributions from the electrons and nuclear binding energy. The atomic mass of atoms, ...

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 or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...

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 conside ...

Type locality

The type locality is the Blagill Mine, Nent Valley, Alston Moor 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 A Site of Special Scientific Interest (SSSI) in Great Britain, or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland, is a conservation designation denoting a protected area in the United Kingdom and Isle ...

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 is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

, associated with

and

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, Alston Moor, 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 Hexham ( ) is a market town and civil parish in Northumberland, England, on the south bank of the River Tyne, formed by the confluence of the North Tyne and the South Tyne at Warden nearby, and close to Hadrian's Wall. Hexham was the administra ...

, Northumberland – minor amounts of barytocalcite have been found here * Russia: Found in

ore of the Tolecheinsli deposit,

Krasnoyarsk Krasnoyarsk is the largest types of inhabited localities in Russia, city and administrative center of Krasnoyarsk Krai, Russia. It is situated along the Yenisey, Yenisey River, and is the second-largest city in Siberia after Novosibirsk, with a p ...

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

hausmannite Hausmannite is a complex oxide, or a mixed oxide, of manganese containing both Divalent, di- and Trivalent, tri-valent manganese. Its chemical formula can be represented as , or more simply noted as , or , as commonly done for magnetite (), the co ...

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, United States. At the 2020 census, the population was 60,501. The county seat is Chatham. Pittsylvania County is included in the Danville, VA Micropolitan Statistical ...

. Barytocalcite occurs here and is probably the source of

for the formation of the rare

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

kinoshitaliteTracy and Beard (2003) American Mineralogist 88:740 to 747 * US: South Ouray,

Uintah County, Utah Uintah County ( ) is a County (United States), 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, Utah, Vernal. The county was named for the portion of t ...

. Barytocalcite occurs in the dolomitic

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

of the

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

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 (Colorado River), Green River in Colorado, Wyoming, and Utah. The sedimen ...

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