Brianyoungite is a

secondary Secondary may refer to: Science and nature * Secondary emission, of particles ** Secondary electrons, electrons generated as ionization products * The secondary winding, or the electrical or electronic circuit connected to the secondary winding i ...

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

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 ...

. The Commission on New Minerals, Nomenclature and Classification (CNMNC) of the

International Mineralogical Association Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 5000 plus known mineral species. Th ...

(IMA) classifies it as a

carbonate 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 ...

with the formula , but

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 ar ...

groups SO₄ also occupy the carbonate CO₃ positions, in the ratio of about one sulfate to three carbonates, so other sources give the formula as , and Gaines et al. classify the mineral as a compound carbonate. It is similar in appearance to

hydrozincite Hydrozincite, also known as zinc bloom or marionite, is a white carbonate mineral consisting of Zn5( CO3)2( OH)6. It is usually found in massive rather than crystalline form. It occurs as an oxidation product of zinc ores and as post mine incru ...

, another zinc carbonate. It was discovered in 1991 and designated IMA1991-053. In 1993 it was named "brianyoungite" after Brian Young (born 1947), a field geologist with the

British Geological Survey The British Geological Survey (BGS) is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS h ...

, who provided the first specimens.

Appearance

The mineral occurs as tiny rosettes less than 100 µm across, composed of thin blades just one or two micrometers across, elongated parallel to the b

crystal axis In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns t ...

, and tapering to a sharp point. The crystals are white and transparent to translucent, with a vitreous

lustre Lustre or Luster may refer to: Places * Luster, Norway, a municipality in Vestlandet, Norway ** Luster (village), a village in the municipality of Luster * Lustre, Montana, an unincorporated community in the United States Entertainment * '' ...

and a white streak.

Structure

The mineral belongs in the

orthorhombic crystal system In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

, or the

monoclinic 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 s ...

with β (the angle between the a and c crystal axes) close to 90^o. The

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 ...

is unknown, but assumed to be either P2₁/m, P21 or P2221. The structure is similar to that of

. There are four formula units 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 ...

(Z = 4) and the lengths of the sides of the unit cell are a = 15.724 Å, b = 6.256 Å and c = 5.427 Å.

Physical properties

Brianyoungite is a soft mineral with

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 th ...

similar to

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 ...

, only 2 to according to some sources, but others say that the hardness is not determinable. It is fairly dense, with

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 (molecule), wa ...

3.93 to 4.09, similar to that of celestine. Cleavage is perfect perpendicular to the a crystal axis (perfect on ) and possible perpendicular to the c crystal axis (possible on ). It is readily soluble with effervescence in acids.

Optical properties

The mineral is

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 ...

, 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_ω = 1.635 and n_ε = 1.650 and maximum

birefringence Birefringence 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 said to be birefringent (or birefractive). The birefring ...

δ = 1.635. It exhibits straight extinction. It is not fluorescent.

Occurrence

The type locality is the Bloomsberry Horse level of the Brownley Hill mine,

Nenthead Nenthead ( ) in the county of Cumbria is one of England's highest villages, at around . It was not built until the middle of the 18th century and was one of the earliest purpose-built industrial villages in Britain. History Nenthead was a ma ...

, Alston Moor District, North Pennines, North and Western Region (Cumberland), Cumbria, England. The type material is conserved at the

Royal Museum of Scotland The National Museum of Scotland in Edinburgh, Scotland, was formed in 2006 with the merger of the new Museum of Scotland, with collections relating to Scottish antiquities, culture and history, and the adjacent Royal Scottish Museum (opened in ...

, Edinburgh, Scotland, 1992.17.1–8.
Brianyoungite occurs with

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. ...

on rubbly

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 ...

in the oxidised zone of Brownley Hill Mine, and on specimens from the nearby Smallcleugh mine. It may be a secondary post-mining mineral. At the type locality it is associated with

smithsonite Smithsonite, also known as zinc spar, is the mineral form of zinc carbonate ( Zn CO3). Historically, smithsonite was identified with hemimorphite before it was realized that they were two different minerals. The two minerals are very similar in app ...

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...

and

goethite Goethite (, ) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the "α" polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient t ...

References

{{reflist Zinc minerals Carbonate minerals Monoclinic minerals Minerals in space group 12 Minerals described in 1993