Oxammit

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Oxammit
General and classification
other names

Guañapit

chemical formula (NH 4 ) 2 (C 2 O 4 ) • H 2 O
Mineral class
(and possibly department) 		Organic compounds / oxalates
System no. to Strunz
and to Dana 		10.AB.55 ( 8th edition : IX / A.01)
50.01.05.01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-disphenoidal, 222
Space group P 2 1 2 1 2
Lattice parameters a  = 8.035  Å ; b  = 10.31 Å; c  = 3.801 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) 1.5
Cleavage clearly after {001}
colour colorless, yellowish-white
Line color White
transparency transparent to opaque
shine Please complete!
Crystal optics
Refractive indices n α  = 1.483
n β  = 1.547
n γ  = 1.595
Birefringence δ = 0.157
Optical character biaxial negative
Other properties
Chemical behavior easily soluble in water

Oxammite (also guañapite ) is an extremely rare mineral from the mineral class of " organic compounds ". It crystallizes in the tetragonal crystal system with the chemical composition (NH 4 ) 2 (C 2 O 4 ) · H 2 O, so it is chemically an ammonium oxalate .

Oxammit usually develops colorless to pale yellow powdery masses. Individual, well-defined crystals are rare. The line color of the mineral is white and with a Mohs hardness of 2.5 it is one of the more soft minerals.

Etymology and history

Oxammit was first described in 1870 by the American mineralogist Charles Upham Shepard (1804-1886). The name is derived from the English chemical name " Ox alate of Amm onia".

The synonymous name Guañapit is derived from the name of the type locality Isla Guañape .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the oxammite belonged to the mineral class of "organic compounds" and there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 , stepanovite , Weddellite , wheatleyite , whewellite , zhemchuzhnikovite and Zugshunstit- (Ce) formed the independent "group of oxalates ".

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 oxammite to the class of "organic compounds" and 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 forms the oxammite group 10.AB.55 .

The systematics of minerals according to Dana also assigns the oxammite to the class of "organic minerals" and there in the department of the same name. Here he is the only representative in the unnamed group 50.01.05 within the sub-section " Salts of organic acids (oxalates) ".

Crystal structure

Oxammite crystallizes orthorhombically in the space group P 2 1 2 1 2 and with the lattice parameters a  = 8.035  Å ; b  = 10.31 Å; c  = 3.801 Å, as well as two formula units per unit cell .

Well-defined, single crystals of oxammite are very rare. Usually the mineral occurs as powdery masses or polycrystalline aggregates of small lamellae.

Education and Locations

Oxammit forms in guano through the excrement of sea birds or bats. It can also develop on rotted eggs or bird carcasses. Due to its good water solubility, the formation is linked to arid climatic conditions . An associated mineral is mascagnin .

So far, only three locations worldwide have been known for Oxammit:

The type material was kept by the University of Virginia , Charlottesville , ( Virginia ) / USA . It was destroyed in a fire in 1916.

See also

Individual evidence

  1. ^ A b 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. 720 .
  2. ↑ a b American Mineralogist Crystal Structure Database - Oxammite .
  3. ↑ American Mineralogist Crystal Structure Database - Oxammite .
  4. ↑ H. Winchell, J. Benoit: Taylorite, Mascagnite, aphthitalite, Leconite and Oxammite from Guano ( PDF 737.1 kB )

literature

Web links