Whewellite

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Whewellite
Whewellite-md82a.jpg
Whewellite crystal from Schlema in the Ore Mountains
General and classification
other names
chemical formula Ca (C 2 O 4 ) • H 2 O
Mineral class
(and possibly department) 		Organic compounds
System no. to Strunz
and to Dana 		10.AB.45 ( 8th edition : IX / A.01)
50.01.01.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / n (No. 14, position 2)Template: room group / 14.2
Lattice parameters a  = 6.29  Å ; b  = 14.58 Å; c  = 10.12 Å
β  = 109.5 °
Formula units Z  = 8
Physical Properties
Mohs hardness 2.5 to 3
Density (g / cm 3 ) measured: 2.21 to 2.23; calculated: 2.22
Cleavage completely after { 1 01};
imperfect after {010};
indistinct after {001} and {110}
Break ; Tenacity clamshell; brittle
colour colorless, white, gray, light yellow, light brown
Line color White
transparency transparent to translucent
shine Glass gloss, pearlescent
Crystal optics
Refractive indices n α  = 1.489 to 1.491
n β  = 1.553 to 1.554
n γ  = 1.649 to 1.650
Birefringence δ = 0.160
Optical character biaxial positive
Axis angle 2V = measured: 80 to 84 °; calculated: 84 °

Whewellite is a rarely occurring mineral from the mineral class of " organic compounds ". It crystallizes in the monoclinic crystal system with the chemical composition Ca (C 2 O 4 ) · H 2 O, so it is chemically a calcium oxalate .

Whewellit usually develops colorless and transparent crystals up to about 20 cm in size with an isometric to short-prismatic habit , but also heart-shaped twins . In the case of polycrystalline formation in massive aggregates, whewellite can also appear white and, through foreign admixtures, also take on a gray, yellowish or brownish color. The line color of the mineral, however, is always white.

Etymology and history

Whewellite was first discovered in the " Glückauf-Schacht " near Burgk in Saxony and described in 1852 by Henry James Brooke (1771–1857) and William Hallowes Miller (1801–1880), who named the mineral after the British philosopher and science historian William Whewell (1794– 1866) named.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Whewellite belonged to the mineral class of "organic compounds" and there to the department of "salts of organic acids", where together with Caoxit , Coskrenit- (Ce) , Glushinskit , Humboldtin , levinsonite (Y) , lindbergite , minguzzite , moolooite , natroxalate , novgorodovaite , oxammite , stepanovite , Weddellite , wheatleyite , zhemchuzhnikovite and Zugshunstit- (Ce) formed the independent "group of oxalates ".

The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also assigns the Whewellite to the class of “organic compounds” and there to the department of “salts of organic acids”. However, this section is further subdivided according to the type of salt-forming acid , so that the mineral can be found according to its composition in the sub-section "Oxalates", where it is the only member of the unnamed group 10.AB.45 .

The systematics of minerals according to Dana also assigns the Whewellite to the class of "organic minerals" and there in the department of the same name. Here he is the only member of the unnamed group 50.01.01 within the subdivision " Salts of organic acids (oxalates) ".

Perfectly formed whewellite crystal from Schlema in the Ore Mountains (size 2.9 cm × 2.8 cm × 2.3 cm)

Crystal structure

Whewellite crystallizes monoclinically in the space group P 2 1 / n (space group no. 14, position 2) with the lattice parameters a  = 6.29  Å ; b  = 14.58 Å; c  = 10.12 Å and β = 109.5 ° and 8 formula units per unit cell . Template: room group / 14.2

Education and Locations

Even if whewellite is the salt of an organic acid, no biological processes have to be involved in its formation. Whewellit forms as rarely occurring primary mineral in low grade hydrothermal carbonate - sulphide - wires or - geodes . Accompanying minerals include calcite , barite , sphalerite , pyrite , Weddellite and waxy hydrocarbons .

As a rare mineral formation, Whewellite could only be detected at a few sites, with around 70 sites (as of 2017) being known to date. In addition to its type locality Burgk, the mineral could also be found in Germany near Freiberg , Schlema and Hartenstein in Saxony; near Peine in Lower Saxony; near Ibbenbüren in North Rhine-Westphalia; in the “Hannebacher Ley” in the Rhineland-Palatinate municipality of Spessart (Brohltal) and near Gera in Thuringia. In Austria, Whewellit has so far only been found on the Graukogel in the Hohe Tauern .

Other locations are in Australia , Brazil , France , Greenland , Italy , Mexico , Romania , Russia , Slovakia , the Czech Republic , Ukraine , Hungary , England in the United Kingdom and in several regions in the United States of America (USA).

Whewellit can crystallize in the urine and lead to the formation of urinary stones . The cause is usually a high intake of oxalic acid or calcium oxalate with food (sorrel, spinach, chard, beetroot, cocoa). In veterinary medicine, whewellite stones are becoming increasingly common, especially in dogs and cats.

See also

literature

  • HJ Brooke, WH Miller: An Elementary Introduction to Mineralogy Longman. Whewellite . Brown, Green, and Longmans, London 1852, pp. 523-524 ( rruff.info [PDF; 153 kB ]).
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 798 (first edition: 1891).
  • Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Villager Nature ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 281 .

Web links

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

Individual evidence

  1. ↑ a b c d e 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.  720 .
  2. ↑ a b c Whewellite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 67  kB ; accessed on August 3, 2017]).
  3. ↑ a b c d e Mindat - Whewellite (English)
  4. ↑ Mindat - Number of localities for Whewellite
  5. ↑ Find location list for Whewellite in the Mineralienatlas and in Mindat
  6. ↑ A. Hesse: Urinary stone types. The origin of the names . In: Animal Stone Letter . tape 13 , no. 7.1 , 2013 ( harnsteinanalysezentrum-bonn.de [PDF; 1.9 MB ; accessed on August 3, 2017]).