Minguzzite
| Minguzzite | |
|---|---|
| General and classification | |
| chemical formula | K 3 Fe 3+ (C 2 O 4 ) 3 • 3H 2 O |
|
Mineral class (and possibly department) |
organic compounds / oxalates |
|
System no. to Strunz and to Dana |
10.AB.25 ( 8th edition : IX / A.01) 50.01.04.01 |
| Similar minerals | Humboldtin |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Room group (no.) | P 2 1 / c (No. 14) |
| Lattice parameters |
a = 7.662 Å ; b = 19.871 Å; c = 10.272 Å β = 105 ° 6 ' Please complete the source as an individual reference |
| Formula units | Z = 4 Please complete the source as an individual reference |
| Physical Properties | |
| Mohs hardness | Please complete |
| Density (g / cm 3 ) | 2.11 |
| Cleavage | completely after {010} |
| colour | yellow-green to green |
| Line color | Please complete |
| transparency | Please complete |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.500 n β = 1.554 n γ = 1.595 |
| Optical character | biaxially negative |
| Other properties | |
| Chemical behavior | soluble in water |
Minguzzite is an extremely rare, secondary mineral from the mineral class of " organic compounds ". It crystallizes in the monoclinic crystal system with the composition K 3 Fe 3+ (C 2 O 4 ) 3 · 3H 2 O, so it is chemically an oxalate . Minguzzite is formed by the decomposition of limonite . The only previously known site is the island of Elba , although the crystals found were microscopic.
Special properties
Like most oxalates, minguzzite decomposes when heated. First of all, the water of crystallization is released and at temperatures above 150 ° C it disintegrates with the formation of iron (III) oxide , potassium carbonate , carbon dioxide and carbon monoxide . The reaction essentially corresponds to the decomposition of iron (II) oxalate . Due to its extreme rarity, many parameters, such as hardness, have not yet been determined. The optical properties and some of the crystallographic properties were determined on synthetic crystals.
Due to its water solubility and low thermal stability, minguzzite is not very stable as a mineral.
Etymology and history
Minguzzite was discovered in 1955 by Garavelli in Capo Calamita ( Elba Island / Italy ). He named the mineral in honor of Carlo Minguzzi (* 1910- † 1953), an Italian mineralogist and professor at the University of Padua . The type material is kept by the University of Florence .
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the minguzzite 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 , natroxalate , novgorodovaite , oxammite , 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 the minguzzite to the class of "organic compounds" and there into 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 representative of the minguzzite group 10.AB.25 .
The systematics of minerals according to Dana also assigns the minguzzite to the class of "organic minerals". Here it is the only mineral within the unnamed group 50.01.04 within the subdivision " Salts of organic acids (oxalates) ".
Education and Locations
Minguzzite was found as a decomposition product of limonite in the type locality and so far the only site (as of 2011) Capo Calamita ( Elba Island ) . It is unclear where the oxalic acid-rich solutions that led to its formation came from.
Crystal structure
Minguzzite crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a = 7.662 Å , b = 19.871 Å, c = 10.272 Å and β = 105 ° 6 'and 4 formula units per unit cell . The crystals found so far had a size of around 0.1 mm with pronounced surfaces according to {010}, {111}, {111} and {110}.
See also
literature
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, Stuttgart 1978, ISBN 3-432-82986-8 , p. 736 .
- Minguzzite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 67 kB )
Web links
Individual evidence
- ↑ A Raman spectroscopic study of thermally treated glushinskite - the natural magnesium oxalate dihydrate. (PDF; 568 kB) In: Spectrochimica acta. Part A. 2004, pp. 643-651 , accessed November 11, 2011 .