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: Greece 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 ...

words for

walnut A walnut is the edible seed of a drupe of any tree of the genus ''Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. Although culinarily considered a "nut" and used as such, it is not a true ...

and

felt Felt is a textile material 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 or acrylonitrile or wood ...

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 pseudohexagonal crystals, commonly as rosettes, up to . It can also be stalactitic,

reniform Reniform is an adjective meaning "kidney-shaped" and may specifically refer to: * Reniform leaf The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single ...

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.

. The mineral forms as a product of

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

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,

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 oxidation states and substitutions: (Mn2+,Fe2+,Mg)(Fe3+,Mn3+)2O4. is a Nordic ...

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

, manganoan calcite,

rhodonite Rhodonite is a manganese silicate minerals, inosilicate, (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 (the name ...

sarkinite Sarkinite, synonymous with chondrarsenite and polyarsenite, is a mineral with formula Mn2(AsO4)(OH). The mineral is named for the Greek word ''σάρκιυος'', meaning made of flesh, for its red color and greasy luster. The mineral was first no ...

, 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 the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...

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, for example) does not necessaril ...

can truly be defined.Guggenheim, p. 163

History

In 1889, caryopilite was discovered from the Harstigen Mine in

Filipstad Filipstad is a 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 Duke Carl Philip (1601&n ...

Värmland County Värmland County (''Värmlands län'') 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 Viken and Innlandet to the west. Prince Carl P ...

, 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 are not chemically bonded. A mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the ...

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 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 decorative s ...

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

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External links

{{Commonscat-inline, Caryopilite Monoclinic minerals Minerals in space group 8 Manganese(II) minerals Magnesium minerals Phyllosilicates Hydroxide minerals