Caryopilite (synonymous with ectropite and ektropite) is a brown-colored mineral with formula (Mn²⁺,Mg)₃Si₂O₅(OH)₄. The mineral was discovered in 1889 from a mine in Sweden. It was named for the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

words for

walnut A walnut is the edible seed of any tree of the genus '' Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. They are accessory fruit because the outer covering of the fruit is technically an i ...

and

felt Felt is a textile that is produced by matting, condensing, and pressing fibers together. Felt can be made of natural fibers such as wool or animal fur, or from synthetic fibers such as petroleum-based acrylic fiber, acrylic or acrylonitrile or ...

in reference to its appearance.

Description

Caryopilite is reddish-brown to tan in color naturally; in thin sections, it is light brown to yellow. The mineral occurs as tabular pseudo hexagonal crystals, commonly as rosettes, up to . It can also be stalactitic,

reniform Reniform is an adjective meaning "kidney-shaped". It may refer to: * Reniform habit, a type of crystal shape * Reniform leaf, a plant leaf shape * Reniform seed, a plant seed shape * Reniform stigma, a spot on the wings of certain moths See ...

with a concentrically radiating structure, or have massive

habit A habit (or wont, as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously. A 1903 paper in the '' American Journal of Psychology'' defined a "habit, from the standpoint of psychology, ...

. The mineral forms as a product of

metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

in manganese-bearing minerals. Caryopilite has been found in association with brandtite,

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 ...

gonyerite The chlorites are the group of phyllosilicate minerals common in low-grade metamorphic rocks and in altered igneous rocks. Greenschist, formed by metamorphism of basalt or other low-silica volcanic rock, typically contains significant amounts o ...

jacobsite Jacobsite is a manganese iron oxide mineral. It is in the spinel group and forms a solid solution series with magnetite. The chemical formula is (Mn,Mg)Fe2O4 or with Redox, oxidation states and substitutions: (Mn2+,Fe2+,Mg)(Fe3+,Mn3+)2O4.

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

manganoan calcite Manganoan calcite or manganocalcite is a variety of calcite rich in manganese, which gives the mineral a pink color.Mang ...

rhodonite Rhodonite is a manganese inosilicate, with the formula (Mn, Fe, Mg, Ca)SiO3, and member of the pyroxenoid group of minerals, crystallizing in the triclinic system. It commonly occurs as cleavable to compact masses with a rose-red color (its na ...

, sarkinite, tirodite.

Structure

Caryopilite consists of triangular islands formed by tetrahedra rings coordinated with sheets containing octahedrally coordinated manganese. The

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

shows some short-range order, but linkages between islands are fully disordered. Thus, no

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 ...

can truly be defined.Guggenheim, p. 163

History

In 1889, caryopilite was discovered from the Harstigen Mine in

Filipstad Filipstad is a Urban areas in Sweden, locality and the seat of Filipstad Municipality, Värmland County, Sweden, with 10,644 inhabitants in 2019. Filipstad was granted city privileges in 1611 by Charles IX of Sweden, who named it after his son Ch ...

Värmland County Värmland County () is a county or '' län'' in west central Sweden. It borders the Swedish counties of Dalarna, Örebro and Västra Götaland, as well as the Norwegian counties of Østfold, Akershus and Innlandet to the west. The title of Duke ...

, Sweden. Hamberg identified it as a new mineral and, on the suggestion of Professor Brögger, named it ''karyopilit''. The name is derived from the

words κάρυον or "walnut", in reference to the mineral's brown color and crystal habit, and πΐλος or "felt", for its appearance under a microscope.Hamberg, p. 27. In 1917, Gust Flink discovered a mineral he named ''ectropite'' (also spelled ektropite) that was most closely related to caryopilite. In 1927, after a new specimen of bementite was discovered that appeared almost identical to caryopilite, it was recommended that caryopilite be invalidated as a mineral species. However, a 1964 study determined that what had been known as bementite was actually a

mixture In chemistry, a mixture is a material made up of two or more different chemical substances which can be separated by physical method. It is an impure substance made up of 2 or more elements or compounds mechanically mixed together in any proporti ...

of two different minerals. Bementite and caryopilite were redefined as distinct species, and caryopilite was made equivalent to ectropite. These changes were accepted by a large majority of the

IMA IMA or Ima may refer to: Education * Indian Military Academy, Dehradun * Instituto Miguel Ángel, a school in Mexico City Galleries and museums * Indianapolis Museum of Art, Indiana, US * Institut du Monde Arabe, Paris, France * Islamic Mus ...

Commission on New Minerals and Mineral Names. In 1980, a study suggested that caryopilite be assigned to the friedelite group rather than the

serpentine group Serpentine subgroup (part of the kaolinite-serpentine group in the category of phyllosilicates) are greenish, brownish, or spotted minerals commonly found in serpentinite. They are used as a source of magnesium and asbestos, and as decorativ ...

Distribution

, caryopilite has been found in Austria, Canada, China, France, Italy, Japan, New Zealand, Norway, Romania, Russia, Slovakia, South Africa, Sweden, the UK, and the US.

References

Bibliography

* *

External links

{{Phyllosilicates Monoclinic minerals Minerals in space group 8 Manganese(II) minerals Magnesium minerals Phyllosilicates Hydroxide minerals