Creedit

from Wikipedia, the free encyclopedia
Creedit
Creedite-112817.jpg
Crystal specimen with colorless and orange Creedit crystals from the Navidad Mine, Abasolo , Municipio de Rodeo, Durango , Mexico (size 6.2 cm × 4.2 cm × 3.9 cm)
General and classification
other names
  • Belijankit
  • Belyankit
chemical formula Ca 3 [Al 2 (F, OH) 10 | SO 4 ] • 2H 2 O
Mineral class
(and possibly department) 		Halides
System no. to Strunz
and to Dana 		3.CG.15 ( 8th edition : III / B.03)
01/12/04/01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / c (No. 15)Template: room group / 15
Lattice parameters a  = 13.94  Å ; b  = 8.61 Å; c  = 9.99 Å
β  = 94.4 °
Formula units Z  = 4
Frequent crystal faces {110}, {111}, { 1 11}, {001}
Physical Properties
Mohs hardness 4th
Density (g / cm 3 ) measured: 2.713 to 2.730; calculated: 2.739
Cleavage completely after {100}
Break ; Tenacity clamshell; brittle
colour colorless, white, orange to reddish, violet to bluish
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.461
n β  = 1.478
n γ  = 1.485
Birefringence δ = 0.024
Optical character biaxial negative
Axis angle 2V = 64 ° 22 ′ (measured); 65 ° (calculated)
Other properties
Chemical behavior easily soluble in acids

Creedit is a rarely occurring mineral from the mineral class of " halides " with the chemical composition Ca 3 [Al 2 (F, OH) 10 | SO 4 ] · 2H 2 O and therefore, chemically speaking, a water-containing calcium - aluminofluoride with additional sulfate ions . The fluorine or hydroxide ions in the round brackets can represent each other in the formula ( substitution , diadochy), but are always in the same proportion to the other constituents of the mineral.

Creedit crystallizes in the monoclinic crystal system and usually develops prismatic, leafy or needle-like crystals with a glass-like sheen on the surfaces, which can be arranged in radial, drusy or granular mineral aggregates . In its pure form, the mineral is colorless and transparent, but it can appear white due to multiple light refraction due to polycrystalline formation or lattice construction defects and can take on an orange to reddish or violet to bluish color due to foreign admixtures, whereby its transparency decreases accordingly. However, its line color is always white.

Etymology and history

Creedit was first discovered together with Gearksutit in 1915 on the spoil dump of the "Colorado Fluorspar Co. Mine" located in the Wagon Wheel Gap of Mineral County (Colorado). Esper S. Larsen and Roger C. Wells described the mineral in 1916 and named it after the town of Creede near where it was found .

Type material of the mineral is available from Harvard University in Cambridge, Massachusetts under catalog no. 81273 and in the National Museum of Natural History in Washington, DC under catalog no. 93117 and C1034 kept.

classification

Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Creedite belonged to the mineral class of the "halides" and there to the department of the "double halides", where it together with Boldyrevit (discredited 2006), Chukhrovit , Elpasolith , Gearksutit , Jarlite , cryolite , cryolithionite , tikhonenkovite , usovite and yaroslavite the "cryolite-elpasolite group" with the system no. III / B.03 formed.

In the last revised and updated Lapis mineral directory by Stefan Weiß in 2018 , which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. III / C.01-40 . In the "Lapis system" this corresponds to the section "Double halides (mostly with OH, H 2 O)", where Creedite together with Acuminite , Artroeit , Chukhrovit- (Ca) , Chukhrovit- (Y) , Chukhrovit- (Ce) , Chukhrovit- (Nd) , Gearksutit, Jakobssonit , Leonardsenit , Meniaylovit and Tikhonenkovite form an independent but unnamed group.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also assigns Creedit to the “halides” class, but in the “complex halides” department. This is also further subdivided according to the crystal structure, so that the mineral according to its structure in the sub-division of "Aluminofluoride with CO 3 , SO 4 , PO 4 " is to be found where it is the only member of the unnamed group 3.CG.15 forms .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also assigns Creedit to the class of "halides" and there in the department of "halide compounds". Here he is to be found as the only member in the unnamed group 01/12/04 within the sub-section “ Halide compounds with various anions ”.

Crystal structure

Creedit crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a  = 13.94  Å ; b  = 8.61 Å; c  = 9.99 Å and β = 94.4 ° and 4 formula units per unit cell . Template: room group / 15

The crystal structure consists of dimers of AlF 4 (OH) 2 - octahedra , which are linked to each other via common edges with Ca [8] cubes and form layers parallel (100). These layers are carried SO 4 - tetrahedra and Ca [8] connected cube.

Modifications and varieties

A mineral discovered and first described by Moisei D. Dorfman in Kazakhstan in 1950, which he named in honor of Dmitrii Stepanovich Belyankin ( Russian: Дмитрий Степанович Белянкин , 1876–1953) as Belyankite (also Beljankite ), emerged as a variety of Creysenedite of Creysenedite in later Neuanalysis . As a result, Belyankit was discredited in 1954.

Education and Locations

Blue-violet Creedit from the "Aqshatau Mine", Aqschatau , Karagandy , Kazakhstan (size: 4.7 × 4.5 × 2.8 cm)

Creedite forms in hydrothermal deposits rich in fluorite . The type material was found in the form of white to colorless grains and little developed crystals up to about 5 millimeters in size, embedded in matt white kaolinite and a little barite . Later, reddish crystals several centimeters in size were also found in the deposit of the Wagon Wheel Gap.

As a rare mineral formation, Creedit could only be detected at a few localities, with slightly more than 50 localities being documented (as of 2018). In addition to its type locality Colorado Fluorspar Co. Mine, the mineral occurred in the United States in the "Henderson Mine" ( Clear Creek County ), also located in Colorado, and in the "Cresson opencast mine" ( Teller County ) as well as in several locations in the states of Arizona, California, Nevada and New Mexico on.

Santa Eulalia in the municipality of Aquiles Serdán in the Mexican state of Chihuahua , where rich Druze was found, is known for its extraordinary Creedit finds . Very well developed and up to three centimeters long crystals also emerged in the " Aqschatau Mine" in Kazakhstan.

Other locations include Bolivia, China, France, Greece, Italy, South Africa and Tajikistan.

See also

literature

  • Esper S. Larsen, Roger C. Wells: Some Minerals from the Fluoritebarite vein near Wagon Wheel Gap, Colorado . In: US Geological Survey (Ed.): Proceedings of the National Academy of Sciences of the United States of America . tape 2 . Washington DC 1916, p. 360–365 (English, rruff.info [PDF; 347 kB ; accessed on January 2, 2019]).
  • SG Gordon: New species . In: American Mineralogist . tape 1 , 1916, p. 86–88 ( rruff.info [PDF; 170 kB ; accessed on January 2, 2019]).
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 493 (first edition: 1891).

Web links

Commons : Creedite  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ a b c d e f Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  167 (English).
  2. ↑ David Barthelmy: Creedite MineralData. In: webmineral.com. Accessed January 2, 2019 .
  3. ↑ a b c d e f g Creedite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 67  kB ; accessed on January 2, 2019]).
  4. ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  5. ↑ a b c d e Mindat - Creedite
  6. ↑ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 420 .
  7. ↑ Esper S. Larsen, Roger C. Wells: Some Minerals from the Fluoritebarite vein near Wagon Wheel Gap, Colorado . In: US Geological Survey (Ed.): Proceedings of the National Academy of Sciences of the United States of America . tape 2 . Washington DC 1916, p. 360–365 (English, rruff.info [PDF; 347 kB ; accessed on January 2, 2019]).
  8. ↑ Catalog of type mineral specimens - C. (PDF 127 kB) In: smmp.net. Commission on Museums (IMA), December 12, 2018, accessed on March 17, 2019 (English, Creedite p. 24).
  9. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed April 25, 2019 .
  10. ^ Igor V. Pekov: Minerals first discovered on the territory of the former Soviet Union . 1st edition. Ocean Pictures, Moscow 1998, ISBN 5-900395-16-2 , pp. 359 .
  11. ^ Karl Hugo Strunz , Christel Tennyson : Mineralogical tables . 8th edition. Academic publishing company Geest & Portig KG, Leipzig 1982, p.  508 .
  12. ↑ Svetlana N. Nena Sheva: Minerals Named in Honor of the Collaborators of the AE Fersman Mineralogical Museum . In: New Data on Minerals . tape 40 . Ocean Pictures Ltd., Moscow 2005, ISBN 5-900395-62-6 , pp. 130 (English, fmm.ru [PDF; 6.6 MB ; accessed on January 2, 2019]).
  13. ^ Michael Fleischer : Probable identity of Belyankite with Creedite . In: American Mineralogist . tape  37 , no. 9-10 , 1952, pp. 785–790 (English, minsocam.org [PDF; 298 kB ; accessed on January 2, 2019]).
  14. ↑ Michael Fleischer : New mineral names; Discredited Minerals; New data . In: American Mineralogist . tape  39 , no. 3-4 , 1954, pp. 402–408 (English, rruff.info [PDF; 383 kB ; accessed on January 2, 2019]).
  15. ↑ a b Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Dörfler Natur ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 68 .
  16. ↑ Number of locations for Creedit. In: mindat.org. Hudson Institute of Mineralogy, accessed January 2, 2019 .