Frondelit
| Frondelit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Mn 2+ Fe 3+ 4 [(OH) 5 | (PO 4 ) 3 ] |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.BC.10 ( 8th edition : VII / B.10) 09/41/02/02 |
| Similar minerals | Rockbridge (iron analog) |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-disphenoidic; 222 |
| Space group | B 22 1 2 (No. 20, position 3) |
| Lattice parameters | a = 13.810 Å ; b = 17.968 Å; c = 6.182 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 4.5 |
| Density (g / cm 3 ) | measured: 3.453; calculated: 3.35 |
| Cleavage | completely after {100}, clear after {010}, indistinct after {001} |
| Break ; Tenacity | uneven |
| colour | dark brown, ocher, red brown, orange, green brown |
| Line color | green (oxidized); brown (unoxidized) |
| transparency | little translucent |
| shine | Glass gloss to matt |
| Crystal optics | |
| Refractive indices |
n α = 1.860 n β = 1.880 n γ = 1.893 |
| Birefringence | δ = 0.033 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 45 ° |
| Pleochroism | X = light yellow brown, Y = Z = brown orange |
| Other properties | |
| Chemical behavior | soluble in hydrochloric acid |
Frondelit is a rare mineral from the mineral class of phosphates , arsenates and vanadates . It crystallizes in the orthorhombic crystal system with the chemical composition Mn 2+ Fe 3+ 4 [(OH) 5 | (PO 4 ) 3 ], so it is a manganese - iron- phosphate.
Frondelit typically forms needle-like crystals up to 8 cm in size. They are not very translucent, but not completely opaque and from brown to orange in color. Oxidized frondelite turns green.
With a Mohs hardness of 4.5, Frondelit is one of the medium-hard minerals, it can just be scratched with a pocket knife. Its hardness is somewhere between fluorite (fluorspar) and apatite .
Etymology and history
The mineral was found by Marie Louise Lindberg-Smith (1918-2005) in 1947 while analyzing rock collected by William T. Pecora in 1945 in the state of Minas Gerais of Brazil . When it was published in 1949, she named it after the American mineralogist Clifford Frondel (1907-2002), who had briefly described Rockbridgeit . Rockbridge forms a mixed crystal row with Frondelit .
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Frondelit belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates, with foreign anions F, Cl, O, OH", where he and Rockbridgeit formed the unnamed group VII / B.10 .
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 Frondelit to the category of “phosphates, etc. with additional anions; without H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the additional anions to the phosphate, arsenate or vanadate complex, so that the mineral according to its composition is classified in the subsection “With only medium-sized cations; (OH etc.): RO 4 > 1: 1 and <2: 1 "can be found, where together with Rockbridgeit and Plimerit the now named" Rockbridgeitgruppe "with the system no. 8.BC.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Frondelit to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here he is in the " Rockbridge group " named after him with the system no. 41.09.02 within the subsection "Anhydrous phosphates etc., with hydroxyl or halogen with (AB) 5 (XO 4 ) 3 Z q ".
Chemism
In Frondelite is partially indicated in the formula, that divalent iron manganese substitute can. Since Frondelit, however, forms a mixed crystal row with rock bridging, which in with the formula Fe 2+ Fe 3+ 4 [(OH) 5 | (PO 4 ) 3 ] (or even (Fe 2+ , Mn 2+ ) Fe 3+ 4 [(OH) 5 | (PO 4 ) 3 ]) crystallizes, it is more likely that manganese-containing forms are referred to as frondelite and more iron-containing forms as rockbridge.
Crystal structure
Frondelite crystallizes orthorhombically in space group B 22 1 2 (space group no. 20, position 3) with the lattice parameters a = 13.810 Å , b = 17.968 Å and c = 6.182 Å as well as four formula units per unit cell .
properties
Frondelit dissolves in hydrochloric acid and also a little in sulfuric acid . It is insoluble in nitric acid .
Modifications and varieties
Rockbridge and Frondelit form a mixed crystal row.
Education and Locations
Frondelite is formed as a secondary mineral in the presence of primary phosphates in pegmatite rock . It is communalized with triphyline , vivanite , heterosite , purpurite , cyrilovite , phosphosiderite and leukophosphite .
The type locality is in the Brazilian state of Minas Gerais and there in Galiléia . There are also other locations in Brazil, including in the state of Paraíba .
In Germany there are only places where Frondelit was found in Bavaria . One of them is in Lower Bavaria , in Rabenstein . Further locations can be found in the Upper Palatinate in Auerbach , Pleystein and Hagendorf .
In Europe there are also sites in western Finland , in the Occitania region in France , in the Portuguese districts of Guarda , Viana do Castelo and Viseu . In Sweden , the mineral can be found in Lapland , in the Czech Republic in the provinces of Bohemia and Moravia . In the United Kingdom , the mineral is found in Cornwall ( England ).
Frondelit can also be found in the Democratic Republic of the Congo , Morocco , Namibia , Rwanda and the US states of California , New Hampshire , North Carolina and South Dakota .
See also
literature
- Marie Louise Lindberg: Crystal habit of frondelite, Sapucaia pegmatite mine, Minas Gerais, Brazil . In: US Geological Survey (Ed.): United States Geological Survey professional paper . Washington DC 1960, p. 195 .
- GJ Redhammer, G. Roth, G. Tippelt, M. Bernroider, W. Lottermoser, G. Amthauer, R. Hochleitner: Manganoan rockbridgeit Fe 4.32 Mn 0.62 Zn 0.06 (PO 4 ) 3 (OH) 5 : structure analysis and 57 Fe Mössbauer spectroscopy . In: Acta Crystallographica . 2006, p. 24-28 .
- Ray L. Frosta, Yunfei Xi, Ricardo Scholz, Fernanda M. Belotti, Martina Beganovic: SEM – EDX, Raman and infrared spectroscopic characterization of the phosphate mineral frondelite (Mn 2+ ) (Fe 3+ ) 4 (PO 4 ) 3 ( OH) 5 . In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy . tape 110 , 2013, p. 7–13 , doi : 10.1016 / j.saa.2013.02.008 .
- MD Dyar, ER Jawin, E. Breves, G. Merchand, MD Lane, SA Mertzmann, DL Bish, JL Bishop: Mössbauer parameters of iron in phosphate minerals: Implications for interpretation of martian data . In: American Mineralogist . tape 99 , 2014, pp. 914-942 .
Web links
- Webmineral - Frondelite
- Database-of-Raman-spectroscopy - Frondelite (database, contains among other things further literature)
- American-Mineralogist-Crystal-Structure-Database - Frondelite (crystal structure database )
Individual evidence
- ↑ The New IMA List of Minerals (as of December 2014)
- ↑ a b c d e f g h Frondelite . 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; 63 kB ; accessed on May 28, 2018]).
- ↑ a b c Mindat - Frondelite (English)
- ^ Mineral Atlas: Frondelit
- ^ Philippe Roth: Minerals first discovered in Switzerland and minerals named after Swiss individuals . 1st edition. Kristallografik Verlag, Achberg 2007, ISBN 3-9807561-8-1 , p. 98 .
- ↑ a b c Marie Louise Lindberg: Frondelite and the frondelite-rockbridge series . In: American Mineralogist . Mineralogical Society of America, 1949, pp. 541–549 ( rruff.info [PDF; 556 kB ; accessed on May 28, 2018]).
- ↑ a b c List of localities for Frondelit in the Mineralienatlas and Mindat