Zugshunstit- (Ce)
| Zugshunstit- (Ce) | |
|---|---|
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|
| General and classification | |
| other names |
IMA 1996-055 |
| chemical formula | (Ce, Nd, La) Al (SO 4 ) 2 (C 2 O 4 ) • 12H 2 O |
|
Mineral class (and possibly department) |
Organic compounds |
|
System no. to Strunz and to Dana |
10.AB.75 ( 8th edition : IX / A.01) 50.01.09.02 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / c (No. 15) |
| Lattice parameters |
a = 8.718 Å ; b = 18.313 Å; c = 13.128 Å β = 93.90 ° |
| Formula units | Z = 4 |
| Frequent crystal faces | {010}, {012}, {111} |
| Physical Properties | |
| Mohs hardness | not definable |
| Density (g / cm 3 ) | 2.121 (calculated) |
| Cleavage | indistinct after {010} |
| Break ; Tenacity | brittle; uneven |
| colour | pale pink (incandescent light) to creamy white, pale blue (fluorescent light) |
| Line color | colorless (i.e. white) |
| transparency | semi-transparent, crystal clear-transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.455 n β = 1.485 n γ = 1.528 |
| Birefringence | δ = 0.073 |
| Optical character | biaxial positive |
| Axis angle | 2V = 85 ° (measured), 82 ° (calculated) |
| Other properties | |
| Chemical behavior | easily soluble in water |
| Special features | alexandrite-like color change in different types of light; rapid decay under the electron beam |
Zugshunstit- (Ce) is a very rarely occurring mineral from the mineral class of " organic compounds ". It crystallizes in the monoclinic crystal system with the chemical formula (Ce, Nd, La) Al (SO 4 ) 2 (C 2 O 4 ) · 12H 2 O, and is thus chemically seen a crystal water-containing cerium - aluminum - sulphate - oxalate .
Zughunstite (Ce) of the type locality forms isometric to blocky, slightly parallel [100] stretched crystals up to almost 2 mm in size with a very characteristic morphology, furthermore subparallel aggregates up to 2 mm in diameter.
The mineral comes from "Alum Cave Bluff", a popular tourist attraction in Great Smoky Mountains National Park, Tennessee, where it is formed from the weathering of a pyrite-containing phyllite . The name can be translated as "Alaunhöhlenteilklippe", but there is no cave here, only the above-mentioned, approx. 30 m high cliff, which forms a 10 m deep overhang, protecting the water-soluble sulfate and oxalate minerals formed here .
Etymology and history
In 1981 T. Dennis Coskren from Columbia , Maryland began investigating an unusual mineralization at the "Alum Cave Bluff". These investigations led to the identification of a large number of unusual minerals typical of an evaporation environment. However, some phases could not be characterized initially and were given to the Mineralogical Laboratory at the University of Michigan for identification, where it was found that three of these phases are rare metal and sulfate-containing oxalates. All three were recognized after submission to the International Mineralogical Association (IMA), including the mineral confirmed under the number IMA 1996-055, which was discovered in 2001 by a US research team with Roland C. Rouse , Donald R. Peacor , Eric J. Essene , T. Dennis Coskren and Robert J. Lauf in the American science magazine "Geochimica et Cosmochimica Acta" was described as Zugshunstit- (Ce).
The mineral was named after the name of the Cherokee Indians for the Great Smoky Mountains belonging to the Appalachians , which can be reproduced as "Tsu-g-shv-sdi". The Levinson Modifier [the suffix "- (Ce)"] indicates the dominant rare earth metal (here: Cer), as the IMA guidelines require when naming minerals containing rare metals .
The type material for Zugshunstit- (Ce) is at the University of Michigan , Ann Arbor / Michigan , and the Smithsonian Institution belonging to National Museum of Natural History , Washington, DC , kept.
classification
In the meanwhile outdated, but still in use 8th edition of the mineral systematics according to Strunz , the Zugshunstit- (Ce) belonged to the mineral class of the "organic compounds" and there to the department of the "salts of organic acids", where together with Caoxit , Coskrenit- (Ce ) , Glushinskit , Humboldtin , Levinsonit- (Y) , Lindbergit , Minguzzit , Moolooit , Natroxalat , Novgorodovait , Oxammit , Stepanovit , Weddellite , Wheatleyite , Whewellit and Zhemchuzhnikovit the independent "group of oxalates " 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 Zughunstit- (Ce) to the class of "organic compounds" and there to the department of "salts of organic acids" a. 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.75 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Zugshunstite (Ce) to the class of "organic minerals" and there in the department of the same name. Here it is with Coskrenit- (Ce) and Levinsonit- (Y) in the "Zugshunstite group" named after im with the system no. 50.01.09 within the sub-section “ Salts of organic acids (oxalates) ”.
Chemism
Mean values from microprobe analyzes of Zugshunstite (Ce) from the “Alum Cave Bluff” led to contents of 2.16% La 2 O 3 , 13.17% Ce 2 O 3 , 1.68% Pr 2 O 3 , 6.50 % Nd 2 O 3 , 0.80% Sm 2 O 3 , 0.27% Eu 2 O 3 , 0.14% Gd 2 O 3 , 6.92% Al 2 O 3 , 1.11% Fe 2 O 3 , 0.04% CaO, 24.01% SO 3 , [10.80]% C 2 O 3 and [32.41]% H 2 O (the last two were calculated from stoichiometry). This resulted in the empirical formula (Ce 0.54 Nd 0.26 La 0.09 Pr 0.07 Sm 0.03 Eu 0.01 Gd 0.01 ) Σ = 1.01 Al 1.00 (SO 4 ) 2 , 00 (C 2.00 O 4 ) · 12.00H 2 O, which has been simplified to (Ce, Nd, La) Al (SO 4 ) 2 (C 2 O 4 ) · 12H 2 O.
Zugshunstite- (Ce) is the cerdominant analogue of the yttrium-dominated Levinsonite- (Y), both of which occur side by side in the “Alum Cave Bluff”. The rare earth metals exhibit strong fractionation between these two minerals. The light rare earth metals (English: "Light Rare Earth Elements", LREE) cerium and praseodymium are concentrated in Zugshunstit- (Ce), neodymium is contained in both oxalates, while yttrium and the medium to heavy rare earth metals ("Medium Rare Earth Elements") and "Heavy Rare Earth Elements", MREE and HREE) Samarium , Europium , Gadolinium , Dysprosium and Erbium are bound to Levinsonite- (Y).
Crystal structure
Zughunstit- (Ce) crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a = 8.718 Å ; b = 18.313 Å; c = 13.128 Å and β = 93.90 ° as well as four formula units per unit cell .
The structure of Zugshunstit- (Ce) is based on a basic building block, namely chains of alternating REE polyhedra and oxalate groups, one oxalate group having edges in common with the neighboring polyhedra. The basic building block is completed by two sulfate tetrahedra , each of which shares a corner with the REE polyhedron. The REE polyhedron in Zugshunstit- (Ce) is a [9] fold-coordinated, i. H. Crowned antiprism with nine ligands and a square cross-section that resembles the polyhedra in monazite. The additional ligand to the top of the antiprism, a water molecule, resulting in displacements of the chains, isolated molecules of water and isolated Al (H 2 O) 6 - octahedron compared to their positions in the very similar structure of the Levinsonit- (Y). The Al octahedra unusually have only H 2 O ligands, and none of them are linked to any other polyhedron of the structure. These are isolated units that are only linked to the basic building blocks via hydrogen bonds .
properties
morphology
Zugshunstit- (Ce) forms idiomorphic, typically isometric to blocky crystals up to almost 2 mm in size, which are reminiscent of blocky feldspar crystals in terms of crystal dress and crystal habit . The crystals are stretched slightly parallel to the a-axis [100] and show the prism {012} as the supporting form. The pinacoid {010} and the prism {111} are subordinately developed . Often the crystals come together to form subparallel aggregated structures.
physical and chemical properties
Zugshunstite (Ce) crystals show - like Coskrenite (Ce), only a little less intensely - alexandrite-like color effects with pale blue-gray coloring in the fluorescent light of the fluorescent tubes and white color in the light of incandescent lamps, which are due to the cerium content. The crystals are colorless in sunlight. Their line color is indicated as colorless. Since the line color corresponds to the powder color and the mineral powder cannot be colorless, the color of the line should best be described as white. The surfaces of the crystal-clear-transparent crystals show a clear glass-like sheen .
The mineral shows imperfect cleavage after {010}, but breaks due to its brittleness similar to amblygonite , whereby the fracture surfaces are uneven. Because of the small crystal size, neither its Mohs hardness nor Vickers hardness could be determined. Measured values for the density of the Zugshunstit- (Ce) do not exist, the calculated density for the mineral is 2.121 g / cm³.
Zugshunstit- (Ce) is easily soluble in water without leaving any residue.
Education and Locations
As a very rare mineral formation, Zugshunstite (Ce) could only be described from one point of discovery so far (as of 2016). Its type locality is the rocky cliff of the "Alum Cave Bluff" in the Great Smoky Mountains National Park, Sevier County , Tennessee , United States . Accompanying minerals are levinsonite (Y), coskrenite (Ce), epsomite and the “hair salt” halotrichite , whereby the Zugshunstite (Ce) occurs either embedded in epsomite and / or halotrichite or forms free-standing crystals in cavities in these minerals.
Zugshunstit- (Ce) is a typical secondary formation that occurs in the soils of the “Alum Cave Bluff”. The name of the location is misleading as it is not a cave but a steep, overhanging rock cliff. The cliff and the surrounding rock form part of the Precambrian Anakeesta Formation, a metapelite with the texture of a phyllite, the main minerals of which are muscovite , biotite , chlorite , quartz and pyrite. This area is extremely rainy with rainfall of 2000 mm per year. The resulting weathering of the rock on the cliff also includes the oxidation of the pyrite and the dissolution of the main rock-forming silicates . This, in turn, leads to sulfate-rich solutions with low pH values that are rich in elements from the dissolved silicates such as iron , magnesium , aluminum , potassium , sodium , calcium and manganese . The rare earth metals probably come from altered phases such as monazite and xenotime . When these solutions drip down the walls of the cliff, they get under the sloping surface of the rock overhang, where partial evaporation leads to the precipitation of sulphates, especially those of iron. Most of the water then continues to the bottom at the base of the cliff, where complete evaporation causes the creation of a wide variety of minerals, mainly hydrated and / or hydrated sulfates. These precipitates consist mainly of epsomite and members of the hair salt family, among which apjohnite is the most common mineral.
use
Due to its rarity, Zugshunstit- (Ce) is only of interest to mineral collectors.
See also
literature
- Zugshunstite- (Ce) . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 68 kB ; accessed on June 29, 2019]).
- Joseph A. Mandarino: New Minerals . In: The Canadian Mineralogist . tape 39 , 2001, p. 1502 , doi : 10.2113 / gscanmin.39.5.1473 ( rruff.info [PDF; 422 kB ; accessed on June 29, 2019]).
- Roland C. Rouse, Donald R. Peacor, Eric J. Essene, T. Dennis Coskren, Robert J. Lauf: The new minerals levinsonite- (Y) [(Y, Nd, Ce) Al (SO 4 ) 2 (C 2 O 4 ) · 12H 2 O] and zugshunstite- (Ce) [(Ce, Nd, La) Al (SO 4 ) 2 (C 2 O 4 ) · 12H 2 O]: Coexisting oxalates with different structures and differentiation of LREE and HREE . In: Geochimica et Cosmochimica Acta . tape 65 , 2001, p. 1101–1115 , doi : 10.1016 / S0016-7037 (00) 00568-8 .
Web links
- Mineral Atlas: Zugshunstite- (Ce) (Wiki)
- David Barthelmy: Zugshunstite- (Ce) Mineral Data. In: webmineral.com. Retrieved June 29, 2019 .
- Zugshunstite- (Ce). In: mindat.org. Hudson Institute of Mineralogy, accessed June 29, 2019 .
- American-Mineralogist-Crystal-Structure-Database - Zugshunstit- (Ce)
Individual evidence
- ↑ a b c d e f g h i j k l m n o p q Roland C. Rouse, Donald R. Peacor, Eric J. Essene, T. Dennis Coskren, Robert J. Lauf: The new minerals levinsonite- (Y ) [(Y, Nd, Ce) Al (SO 4 ) 2 (C 2 O 4 ) .12H 2 O] and zugshunstite- (Ce) [(Ce, Nd, La) Al (SO 4 ) 2 (C 2 O 4 ) · 12H 2 O]: Coexisting oxalates with different structures and differentiation of LREE and HREE . In: Geochimica et Cosmochimica Acta . tape 65 , 2001, p. 1101–1115 , doi : 10.1016 / S0016-7037 (00) 00568-8 .
- ↑ a b Zugshunstite- (Ce) . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 68 kB ; accessed on June 29, 2019]).
- ↑ a b c d e T. Dennis Coskren, Robert J. Lauf: The Minerals of Alum Cave Bluff, Great Smoky Mountains, Tennessee . In: The Mineralogical Record 2000 . tape 31 , 2000, pp. 163-175 .
- ↑ a b c Joseph A. Mandarino: New Minerals . In: The Canadian Mineralogist . tape 39 , 2001, p. 1502 , doi : 10.2113 / gscanmin.39.5.1473 ( rruff.info [PDF; 422 kB ; accessed on June 29, 2019]).
- ^ A b Donald R. Peacor, Roland C. Rous, Eric J. Essene: Coskrenite- (Ce), (Ce, Nd, La) 2 (SO 4 ) 2 (C 2 O 4 ) · 8H 2 O, a new rare-earth oxalate mineral from Alum Cave Bluff, Tennessee: Characterization and crystal structure . In: The Canadian Mineralogist . tape 37 , 1999, pp. 1453–1462 ( rruff.info [PDF; 1.1 MB ; accessed on June 29, 2019]).
- ↑ Catalog of Type Mineral Specimens - Z. (PDF 30 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed June 29, 2019 .
- ↑ Localities for Zugshunstite- (Ce). In: mindat.org. Hudson Institute of Mineralogy, accessed June 29, 2019 .
- ↑ Find location list for Zugshunstit- (Ce) at the Mineralienatlas and at Mindat
- ^ Robert J. Lauf: Secondary Sulfate Minerals From Alum Cave Bluff: Microscopy and Microanalysis . 1st edition. Oak Ridge National Laboratory, Oak Ridge, Tennessee 1997, p. 1–43 ( web.ornl.gov ( Memento from February 14, 2017 in the Internet Archive ) [PDF; 45.5 MB ]).