Carpholite

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Carpholite
Carfolite.jpg
Radial aggregates of needle-like, yellow carpholite crystals. Exhibited in the National Museum in Prague
General and classification
other names

Straw stone

chemical formula
  • Mn 2+ Al 2 [(OH) 4 | Si 2 O 6 ]
  • MnAl 2 [(F, OH) 4 | Si 2 O 6 ]
Mineral class
(and possibly department) 		Silicates and germanates - chain and band silicates (inosilicates)
System no. to Strunz
and to Dana 		9.DB.05 ( 8th edition : VIII / F.03)
65.01.05.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m 2 / m 2 / m
Room group (no.) Ccca (No. 68)
Lattice parameters a  = 13.72  Å ; b  = 20.22 Å; c  = 5.13 Å
Formula units Z  = 8
Twinning after {100}
Physical Properties
Mohs hardness 5 to 5.5 or 5.5 to 6
Density (g / cm 3 ) measured: 2.935 to 3.031; calculated: [3.07]
Cleavage completely after {010}
Break ; Tenacity splintery; very brittle
colour straw yellow to wax yellow, brownish yellow
Line color yellowish white
transparency translucent to opaque
shine Silky gloss
Crystal optics
Refractive indices n α  = 1.610
n β  = 1.628
n γ  = 1.630
Birefringence δ = 0.020
Optical character biaxial negative

Carpholite is a rarely occurring mineral from the mineral class of "silicates and germanates". It crystallizes in the orthorhombic crystal system with the idealized chemical composition Mn 2+ Al 2 [(OH) 4 | Si 2 O 6 ] and is therefore chemically a manganese - aluminum - silicate with additional hydroxide ions .

Carpholite develops fine-needle to prismatic crystals , which are usually arranged in tufted to radial-radial mineral aggregates , which is also the cause of the mineral's silk-like sheen . The crystals themselves are translucent and straw yellow in color, which occasionally turns waxy yellow to brownish yellow. Due to the aggregate formation, however, the mineral appears opaque.

With the iron analogue ferrocarpholite (Fe 2+ Al 2 [(OH) 4 | Si 2 O 6 ]), carpholite forms a seamless series of mixed crystals .

Etymology and history

Karpholite was first discovered near Horní Slavkov (German Schlaggenwald ) in the Czech region of Karlovarský kraj ( Karlsbad , Bohemia) and described in 1817 by Abraham Gottlob Werner . He named the mineral because of its characteristic color and its tufted aggregate form after the ancient Greek words χαρφος karphos for straw and λίθος lithos for stone, hence the German synonym straw stone .

The type material of the mineral is kept in the mineralogical collection of the Technical University of the Bergakademie Freiberg (catalog no. 103027-103038).

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the karpholite belonged to the mineral class of "silicates and germanates" and there to the department of " chain silicates and band silicates (inosilicates) ", where it was named after the "karpholite group" the system no. VIII / F.03 and the other members Balipholit , Ferrokarpholith , Kalikarpholith , Kukisvumit , Lintisit , lorenzenite , Magnesiokarpholith , Manganokukisvumit , Paravinogradovit , Vanadiokarpholith and vinogradovite formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies carpholite in the category of "chain and band silicates (inosilicates)". However, this is further subdivided according to the structure of the chains and the possible presence of additional anions , so that the mineral according to its structure and composition can be found in the subsection “Chain and band silicates with 2-periodic single chains Si 2 O 6 ; with additionally O, OH, H 2 O; Pyroxene-related minerals "can be found, where only together with balipholite, ferrocarpholite, magnesiocarpholite, calicarpholite and vanadiocarpholite, the" carpholite group "with the system no. 9.DB.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns carpholite to the class of "silicates and Germanates" and there in the department of "chain silicate minerals". Here it is together with balipholite, ferrocarpholite, calicarpholite, magnesiocarpholite and vanadiocarpholite in the " carpholite group " with system no. 65.01.05 can be found in the sub-section “Chain Silicates : Simple unbranched chains, W = 1 with chains P = 2”.

Crystal structure

Carpholite crystallizes orthorhombically in the space group Ccca (space group no. 68) with the lattice parameters a  = 13.72  Å ; b  = 20.22 Å and c  = 5.13 Å and 8 formula units per unit cell .

properties

In front of the soldering tube , carpholite puffs up when the flame is held at the ends of the fibers. In addition, the mineral is very brittle and cracks easily with splintering fracture .

Carpholite is also insoluble in concentrated and heated hydrochloric acid .

Education and Locations

Fibrous, silky, shiny carpholite from Biesenrode , Saxony-Anhalt, Germany (field of view 3 cm)

Carpholite forms in the drusen areas of greisen as well as in quartz creaking ( mining for "solid, hard-to- extract rock") from metamorphosed slates. As accompanying minerals may include chloritoid , fluorite manganese, garnet , cassiterite , sudoite and Zinnwaldite occur.

As a rare mineral formation, karpholite could only be detected at a few sites, whereby so far (as of 2014) around 30 sites are known. In addition to its type locality Horní Slavkov (Schlaggenwald), the mineral appeared in the Czech Republic only in the nearby “Huber” shaft near Krásno nad Teplou (German Schönfeld ).

In Germany, karpholite is only known from the Sengelbachtal near Biesenrode and from Wippra (Sangerhausen) in Saxony-Anhalt. The only known location in Switzerland so far is the Tea Alp near Martina GR in the canton of Graubünden.

Other locations include Belgium, China, France, Greece, Italy, Japan, Kazakhstan, Romania, Spain, Turkey, the United Kingdom (UK) and the United States of America (USA).

See also

literature

  • Abraham Gottlob Werner : Karpholite In: Last Mineral System. , Craz and Gerlach and Carl Gerold, Freiberg and Vienna 1817, pp. 43–44 ( PDF 162 kB )
  • Josef Steinmann: Chemical investigation of the carpholite. In: Johann Salomo Christoph Schweigger: Publish a new journal for chemistry and physics in connection with several scholars. Oxford University 1819, pp. 413–424 ( available online in Google Book Search)
  • W. Lindemann, R. Wögerbauer, P. Berger: The crystal structure of karpholite (Mn 0.97 Mg 0.08 Fe II 0.07 ) (A l1.90 Fe III 0.01 ) Si 2 O 6 (OH) 4 . In: New Yearbook for Mineralogy. Months booklet, 1979, pp. 282-287
  • Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 527 .
  • Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 237 ( Dörfler Natur ).

Web links

Commons : Karpholite (Carpholite)  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
  2. ↑ a b c d Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  622 .
  3. ↑ a b c d e Carpholite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 69 kB )
  4. ↑ a b Mindat - Carpholite
  5. ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p.  527 .
  6. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp.  724 (first edition: 1891).
  7. ↑ a b Abraham Gottlob Werner : Karpholith In: Last Mineral System. , Craz and Gerlach and Carl Gerold, Freiberg and Vienna 1817, pp. 43–44 ( PDF 162 kB )
  8. ↑ Type material catalog of the University of Hamburg - Karpholith
  9. ↑ Josef Steinmann: Chemical investigation of the karpholite. In: Johann Salomo Christoph Schweigger: Publish a new journal for chemistry and physics in connection with several scholars. Oxford University 1819, p. 415 ( available online in Google Book Search)
  10. ↑ knauer to knäufeln In: German Dictionary of Jacob and Wilhelm Grimm. , Volume 11, columns 1365 to 1368, Leipzig 1854-1961
  11. ↑ Mindat - Number of localities for carpholite
  12. ↑ Find location list for carpholite ( Carpholite ) at the Mineralienatlas and at Mindat