Wheatleyite

from Wikipedia, the free encyclopedia
Wheatleyite
General and classification
other names

IMA 1984-040

chemical formula Na 2 Cu (C 2 O 4 ) 2 · 2 (H 2 O)
Mineral class
(and possibly department) 		Organic compounds / oxalates
System no. to Strunz
and to Dana 		10.AB.30 ( 8th edition : IX / A.01)
50.01.08.01
Similar minerals Moolooit
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Room group (no.) P 1 (No. 2)
Lattice parameters a  = 7.56  Å ; b  = 9.66 Å; c  = 3.59 Å
α  = 76.6 °; β  = 103.7 °; γ  = 109.1 °
Formula units Z  = 1
Physical Properties
Mohs hardness 1 to 2
Density (g / cm 3 ) 2.27
Cleavage completely after {100}
colour blue
Line color Light Blue
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.400
n β  = 1.499
n γ  = 1.667
Birefringence δ = 0.267
Optical character biaxial positive
Axis angle 2V = 83 ° (measured); 84 ° (calculated)
Other properties
Special features water soluble

Wheatleyite is a very rarely occurring mineral from the mineral class of " organic compounds ". It crystallizes in the triclinic crystal system with the composition Na 2 Cu (C 2 O 4 ) 2 · 2 (H 2 O), so it is chemically a sodium copper oxalate .

The crystals found so far were small, approximately 2 mm large aggregates of blue color.

Etymology and history

The discoverer of Wheatleyite is William W. Pinch , who showed the material from the "Wheatley Mines" in the US state of Pennsylvania to Pete J. Dunn in the early 1980s . The mineral was first described in 1986 by Roland C. Rouse , Donald R. Peacor , Pete J. Dunn, William B. Simmons and Dale Newbury in the US science magazine "The American Mineralogist". The “Wheatley Mines” in the Phoenixville Mining District, Schuylkill Township , Chester Co. , Pennsylvania / USA are considered to be the type locality . The name refers to the place where it was first found. The type material is kept in the Smithsonian Institution ( National Museum of Natural History ), Washington, DC / USA .

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , wheatleyite belonged to the mineral class of "organic compounds" and there to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 , moolooite , minguzzite , natroxalate , novgorodovaite , oxammite , stepanovite , Weddellite , whewellite , zhemchuzhnikovite and Zugshunstit- (Ce) the independent "oxalate group" with the system no. IX / A.01 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 assigns wheatleyite to the class of "organic compounds" and there to the department of "salts of organic acids". However, this division is further subdivided according to the acid on which the compounds are based, so that the mineral can be found according to its composition in the sub-division of "Oxalates", where it is the only member of the unnamed group 10.AB.30 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Wheatleyite to the class of "organic minerals" and there in the department of the same name. Here he is to be found as the only member in the unnamed group 50.10.80 within the sub-section “ Salts of organic acids (oxalates) ”.

Crystal structure

Wheatleyite forms crystals in the triclinic crystal system in space group P 1 (space group no. 2). The lattice parameters are a  = 7.56  Å ; b  = 9.66 Å; c  = 3.59 Å; α = 76.6 °; β = 103.7 ° and γ = 109.1 ° with one formula unit per unit cell .

properties

Like most oxalates, wheatleyite is not thermally stable. Thermal analytical studies have shown that Wheatleyite gives off its water of crystallization at temperatures between 70 and 110 ° C and gradually decomposes from 250 and 350 ° C to form copper (II) oxide , carbon monoxide and carbon dioxide .

Wheatleyite is readily soluble in water and for this reason is not very stable as a mineral.

Education and Locations

Wheatleyite is a secondary mineral, but the formation conditions of the mineral are not yet clearly understood. An anthropogenic or biogenic origin can be ruled out for the type locality Wheatley Mines , as wheatleyite crystals are known that are overgrown by sphalerite . This distinguishes the Wheatleyite z. B. from the chemically similar moolooite , which can arise from the action of bird droppings on copper ores. In addition to sphalerite, wheatleyite can also occur in association with galena , cerussite and quartz .

So far (as of 2012) only one site has become known:

See also

Individual evidence

  1. ^ A b c 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. 719 .
  2. ↑ a b c d Wheatleyite at mindat.org (engl.)
  3. ↑ Handbook of Mineralogy: Wheatleyite ( PDF )
  4. ↑ Roland C. Rouse et al .: Wheatleyite, Na 2 Cu (C 2 O 4 ) 2 · 2H 2 O. - A natural sodium copper salt of oxalic acid. (PDF; 353 kB) In: American Mineralogist. 1986, pp. 1240-1242 , accessed February 1, 2012 .
  5. ↑ Ray L. Frost et al .: Thermogravimetric analysis of wheatleyite Na 2 Cu (C 2 O 4 ) 2 · 2 (H 2 O). (PDF; 317 kB) 2008, pp. 993–997 , accessed on February 1, 2012 .
  6. ^ Mindat: Wheatley Mines

Web links