Pimelite was discredited as a

mineral species In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

by 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) in 2006, in an article which suggests that “pimelite” specimens are probably willemseite (which is approved), or kerolite (which is also discredited). This was a mass discreditation, and not based on any re-examination of the

type material In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

(assuming any exists).Burke (2007) Canadian Mineralogist: 44-6: 1557 Nevertheless, a considerable number of papers have been written, verifying that pimelite is a

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

-dominant

smectite A smectite (from ancient Greek ''σμηκτός'' smektos 'lubricated'; ''σμηκτρίς'' smektris 'walker's earth', 'fuller's earth'; rubbing earth; earth that has the property of cleaning) is a mineral mixtures of various swelling sheet sil ...

.Mindat.org
/ref>Economic Geology (1949) 44:13Economic Geology (2004) 99:1197Faust (1966) American Mineralogist 51:279Manceau and Calas (1985) American Mineralogist 70: 549 It is always possible to redefine a mineral wrongly discredited. The mineral was erroneously assumed to be a nickel-rich

talc Talc, or talcum, is a Clay minerals, clay mineral, composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thi ...

in a paper published in the American Mineralogist in 1979,Brindley, Bish and Wan (1979) American Mineralogist 64:615 but it had already been determined to be a smectite as early as 1938, and this was confirmed in another article in the American Mineralogist in 1966. Both nickel-bearing talc and nickel dominant smectite occur at the type locality, Szklary, Ząbkowice Śląskie County, Lower Silesia, Poland.

Mineral group

According to the literature pimelite belongs to the

group, trioctahedral subgroup. “Smectite” is the name of a group of minerals, not the name of a

. Subgroup members: *

hectorite Hectorite is a rare soft, greasy, white clay mineral with a chemical formula of . Hectorite was first described in 1941 and named for an occurrence in the United States near Hector (in San Bernardino County, California, 30 miles east of Barstow ...

(IMA questionable status) Webmineral data
/ref> * pimelite (IMA discredited) *

saponite Saponite is a trioctahedral mineral of the smectite group. Its chemical formula is . It is soluble in sulfuric acid. It was first described in 1840 by Svanberg. Varieties of saponite are griffithite, bowlingite and sobotkite. It is soft, m ...

* sauconite *

stevensite Stevensite is white clay mineral. The mineral is a member of smectite. The mineral is named after Edwin Augustus Stevens Edwin Augustus Stevens (July 28, 1795 – August 7, 1868) was an American engineer, inventor, and entrepreneur who ...

(IMA questionable status) * yakhontovite * zincsilite Smectite group minerals are

phyllosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

clay minerals Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay mineral ...

. Pimelite apparently constitutes part of the mixtures called

garnierite Garnierite is a general name for a green nickel ore which is found in pockets and veins within weathered and serpentinized ultramafic rocks. It forms by lateritic weathering of ultramafic rocks and occurs in many nickel laterite deposits in the ...

noumeite Garnierite is a general name for a green nickel ore which is found in pockets and veins within weathered and serpentinized ultramafic rocks. It forms by lateritic weathering of ultramafic rocks and occurs in many nickel laterite deposits in the ...

, and it could form a series with stevensite or saponite.

Discovery

Pimelite was discovered in 1788 by

Martin Heinrich Klaproth Martin Heinrich Klaproth (1 December 1743 – 1 January 1817) was a German chemist. He trained and worked for much of his life as an apothecary, moving in later life to the university. His shop became the second-largest apothecary in Berlin, and ...

, and renamed in 1800 by

Dietrich Ludwig Gustav Karsten Dietrich Ludwig Gustav Karsten (5 April 1768 – 20 May 1810) was a German mineralogist. Among the most notable of Karsten's writings is a mineralogy book published in 1789 when he was only 21 years old. In later years Karsten held senior governme ...

( :de:Dietrich Ludwig Gustav Karsten) from the Greek word for fat, in allusion to the appearance.

Structure

It belongs to the

hexagonal crystal system 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 crysta ...

, but the crystal class is unknown. As with all

phyllosilicates Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

, the basic structural element is a triple layer, called a t-o-t layer, where "t" stands for a

tetrahedral In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the o ...

sheet and "o" stands for an

octahedral In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...

sheet. The tetrahedral sheets comprise tetrahedra, linked together in nearly

hexagonal In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A '' regular hexagon'' has ...

rings. Three of the

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

s in each tetrahedron form links to other tetrahedra in the sheet, and the fourth oxygen, the apical oxygen, points away from the sheet. The apical oxygens of one tetahedral sheet face the apical oxygens of the other tetrahedral sheet, forming octahedral sites between the sheets, and this is the octahedral "o" layer. The octahedral sites may be fully occupied by

divalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of an ...

cations 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 ...

, producing trioctahedral layers, where each O or OH ion is surrounded by 3 divalent cations. Alternatively the octahedral sites may be 2/3 occupied by

trivalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Description The combining capacity, or affinity of an ...

, producing dioctahedral layers, where each O or OH ion is surrounded by 2 trivalent cations. There is one formula unit 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 = 1), and the unit cell parameters are a = 5.256 Å and c = 14.822 Å. When treated with

glycol A diol is a chemical compound containing two hydroxyl groups ( groups). An Aliphatic compound, aliphatic diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. The most common ...

the cell expands to 17.35 Å.

Appearance

Pimelite does not form visible crystals. It is fine-grained or fibrous, with the apple green color typical of nickel compounds. It is translucent, with a white streak and a waxy luster.

Optical properties

It is biaxial (-) but it can appear

isotropic Isotropy is uniformity in all orientations; it is derived . Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence ''anisotropy''. ''Anisotropy'' is also used to describe ...

due to its fine grain size. The

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 ...

are N_x = 1.592 and N_y = 1.615. It is

pleochroic Pleochroism (from Greek πλέων, ''pléōn'', "more" and χρῶμα, ''khrôma'', "color") is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light. Backgroun ...

, pale green, and colorless to light yellow green. It is not

fluorescent 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 ...

Physical properties

Pimelite breaks with an uneven to conchoidal

fracture Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displa ...

, but it shows no cleavage. It is soft 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 ...

2 to , similar to that of

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. ...

, and its

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 ...

is 2.23 to 2.98. It is neither

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 consid ...

nor

magnetic Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...

. It is decomposed by

acids In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

Occurrence

Pimelite is found in

lateritic nickel ore deposits Lateritic nickel ore deposits are surficial, weathered rinds formed on ultramafic rocks. They account for 73% of the continental world nickel resources and will be in the future the dominant source for the mining of nickel. Genesis and types of ni ...

above serpentinites or

dunite Dunite (), also known as olivinite (not to be confused with the mineral olivenite), is an intrusive igneous rock of ultramafic composition and with phaneritic (coarse-grained) texture. The mineral assemblage is greater than 90% olivine, with mi ...

s, frequently mixed with

-rich serpentine minerals or

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 form ...

. The type locality is Kosemutz, near Frankenstein, Silesia, Poland, and it has also been found in New Jersey, USA. A nickel

silicate In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...

hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...

mineral was first described from

Franklin, New Jersey Franklin is a borough in Sussex County, in the U.S. state of New Jersey. As of the 2010 United States Census, the borough's population was 5,045Sterling Hill. It was originally called ''desaulesite'', for Major de Saules, manager of the Trotter Mine at Franklin, but that name is now used for

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 ...

-rich

. In 1966 the material was shown to be identical with pimelite. Pimelite from the Trotter Shaft occurs as localized, patchy, thin crusts and dense 1 to 6 cm masses as an alteration product of

arsenides. It 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 ...

, low-temperature mineral, associated with

annabergite Annabergite is an arsenate mineral consisting of a hydrous nickel arsenate, Ni3(AsO4)2·8H2O, crystallizing in the monoclinic system and isomorphous with vivianite and erythrite. Crystals are minute and capillary and rarely met with, the mineral ...

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 ...

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

sphalerite Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...

.http://franklin-sterlinghill.com/dunn/ch18/pimelite.stm>

References

{{Reflist Phyllosilicates Nickel minerals Hexagonal minerals