Dickthomssenit
| Dickthomssenit | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 2000-047 |
| chemical formula | Mg (V 2 O 6 ) • 7H 2 O |
|
Mineral class (and possibly department) |
Oxides (hydroxides, V [5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates) |
|
System no. to Strunz and to Dana |
4.HD.25 ( 8th edition : IV / F.09?) 01.47.04.01 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / c (No. 15) |
| Lattice parameters |
a = 38.954 Å ; b = 7.2010 Å; c = 16.3465 Å β = 97.602 ° |
| Formula units | Z = 16 |
| Physical Properties | |
| Mohs hardness | 2.5 |
| Density (g / cm 3 ) | > 1.96 and <2.09 (measured); 2.037 (calculated) |
| Cleavage | very perfect after {100} |
| Break ; Tenacity | hooked; brittle |
| colour | light golden brown |
| Line color | White |
| transparency | translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.6124 n β = 1.6740 n γ = 1.7104 |
| Birefringence | δ = 0.0980 |
| Optical character | biaxial negative |
| Axis angle | 2V = 74 ° (measured); 2V = 73 ° (calculated) |
| Other properties | |
| Special features | rapid dehydration under the electron beam |
Dickthomssenite is a very rarely occurring mineral from the mineral class of " oxides (as well as hydroxides , V [5,6] - vanadates , arsenites , antimonites, bismutites, sulfites , selenites , tellurites and iodates )". It crystallizes in the monoclinic crystal system with the idealized chemical composition Mg (V 2 O 6 ) 7H 2 O, making it chemically seen a hydrous magnesium - divanadate .
Dickthomssenit forms needle-like crystals up to 0.25 mm long and flat-short prismatic crystals up to 0.5 × 1.5 mm in size, which come together to form radial fibrous aggregates of 5 mm in size, which can cover areas of 1.5 × 2.5 cm.
The type locality of Dickthomssenits is 16 km east of La Sal lying uranium - vanadium - deposit "Firefly Pigmay" ( coordinates of the UV deposit Firefly Pigmay ) in San Juan County , Utah , USA .
Etymology and history
At the turn of the millennium, the mineral collector and hobby mineralogist Joseph Marty from Salt Lake City / Utah, west of the main tunnel of the "Firefly-Pigmay Mine", found a light golden brown mineral in encrustations on sandstone , which he could not identify. After determining the physical properties and the chemical composition as well as intensive X-ray diffractometric and structural investigations by a team of scientists led by John M. Hughes from the Department of Geology at Miami University in Oxford , Ohio , the mineral was given the provisional name by the International Mineralogical Association (IMA) IMA 2000-047 which recognized it as a new mineral in 2000. In 2008, the first scientific description of this mineral was made by a team of US scientists with John M. Hughes , Forrest E. Cureton , Joseph Marty , Robert A. Gault , Mickey E. Gunter , Charles F. Campana , John Rakovan , André Sommer and Matthew E. Brueseke in the Canadian science magazine " The Canadian Mineralogist " as Dickthomssenite ( English Dickthomssenite ). They named the mineral after the American deposit geologist and consulting geologist Richard ("Dick") Wyatt Thomssen (* 1933) from Dayton , Nevada / USA. Thomssen was u. a. Associate Editor of The Mineralogical Record (1978–1988), President and Executive Director of Mineralogical Record, Inc. (1983–1988), and Editor of the International Micromounter's Journal (1994 to date).
The type of material for Dickthomssenit is in the collection of the Smithsonian Institution belonging to National Museum of Natural History , Washington, DC , kept.
classification
The 8th edition of the mineral classification according to Strunz , which is now outdated, but still in use in some cases, does not yet list the Dickthomssenite. He would probably belong to the mineral class "oxides and hydroxides" and then to the family of "Vanadium hydroxides" where he along with Barnesit , Corvusit , Fernandinit , Grantsit , Hendersonit , Hewettit , Metahewettit , Metarossit and Rossit the Rossit-Hewettit group with the system no. IV / F.09 would have 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), assigns thick homssenite to the mineral class of "oxides (as well as hydroxides, V [5,6] -vanadates, arsenites, antimonites, bismuthites, Sulfites, selenites, tellurites and iodates) "and there in the section of" V [5,6] Vanadates ". However, this is further subdivided according to the structure of the vanadate complexes, so that the mineral can be found according to its structure in the subdivision "Chain vanadates (Inovanadates)", where it forms the unnamed group 4.HD.25 as the only member .
The systematics of minerals according to Dana , which is predominantly used in the English-speaking world , assigns the Dickthomssenite, on the other hand, to the class of "phosphates, arsenates and vanadates" and there to the category of "vanadium oxy salts". There he is to be found as the only member in the unnamed group 47.01.04 within the subdivision " Vanadium Oxysalze (Normal VO 3 ) ".
Chemism
Mean values from microprobe analyzes on thick homo-senite from the type locality yielded 15.38% MgO; 0.46% FeO; 73.92% V 2 O 5 and 10.24% H 2 O (determined from the difference to 100%). The empirical formula (Mg 0.94 Fe 0.02 ) Σ = 0.96 V 2 O 6 · 1.4H 2 O was determined from the microprobe analyzes on the basis of two vanadium atoms . Due to the rapid dehydration of thick homssenite under the electron beam, however, the contents of the metals are too high and thus the water content determined by the difference is too low. On the basis of 13 anions (as can be deduced from the structural analysis), on the other hand, the empirical formula (Mg 0.95 Fe 0.02 ) Σ = 0.97 V 2.01 O 6 · 7H 2 O results, which results in Mg (V 2 O 6 ) · 7H 2 O can be idealized and contents of 11.57% MgO; Requires 52.22% V 2 O 5 and 36.21% H 2 O.
Of all known minerals, only okieite , Mg 3 [V 10 O 28 ] · 28H 2 O, has the same combination of elements Mg – V – O – H as thickhomssenite. Chemically similar, however, are u. a. Ammoniolasalite , (NH 4 ) 2 Mg 2 (H 2 O) 20 [V 10 O 28 ]; Bluestreakite , K 4 Mg 2 (V 4+ 2 V 5+ 8 O 28 ) • 14H 2 O; Huemulite , Na 4 Mg (V 10 O 28 ) • 24H 2 O; Lobsterite , K 2 Mg 2 (V 10 O 28 ) • 16H 2 O; Lasalite , Na 2 Mg 2 (V 10 O 28 ) • 20H 2 O; Magnesiopascoite , Ca 2 Mg (V 10 O 28 ) • 16H 2 O; and vanadium-containing adelite , CaMg ([As, V] O 4 ) (OH).
Metarossite, Ca (V 2 O 6 ) 2H 2 O, can be identified as a lower-water Ca-dominant analogue and Ansermetite , Mn 2+ (V 2 O 6 ) 4H 2 O, as a lower- water Mn 2+ -dominant analogue of Mg- conceive of dominated thick homo senite.
Crystal structure
Dickthomssenite crystallizes in the monoclinic crystal system in the space group C 2 / c (space group no.15 ) with the lattice parameters a = 38.954 Å , b = 7.2010 Å, c = 16.3465 Å and β = 97.602 ° as well as sixteen formula units per unit cell . According to recent studies, the unit cell is triclinic and twinned around the a-axis. The monoclinic unit cell from John M. Hughes and colleagues is created by doubling the b-axis and then transforming it.
The crystal structure of Dickthomssenite consists of parallel [010] oriented endless chains of V 2 O 6 divanadate polyhedra with common edges that contain [2 + 3] -coordinated vanadium atoms. These [010] chains are linked in the plane (100) by Mg1 [O 2 (H 2 O) 4 ] octahedra via common corners, their central Mg atom with the oxygen atoms of the divanadate chains and the four undivided vertices of the octahedron, which are formed by the oxygen of the H 2 O molecules, is connected.
| Crystal structure of thick homssenite |
|
| Color legend: __ V __ Mg __ O __ H |
Dickthomssenite has a very perfect cleavage according to {100}, whereby the cleavage surfaces separate successive vanadate-Mg-octahedral layers from one another. The layers in between consist of H 2 O molecules as well as Mg2 (H 2 O) 6 and Mg3 (H 2 O) 6 octahedra, whereby no Mg octahedron is linked to other polyhedra except by hydrogen bonds .
Overall, the structural unit in the thickhomssenite is formed by the two [V 2 O 6 ] dimers and the unit forming the interstices by [ [6] Mg 2 (H 2 O) 10 (H 2 O) 0 ] 4+ , the four being unbound H 2 O molecules complete the unit cell.
properties
morphology
Dickthomssenite is found as a coating on sandstones that contain local organic material including remnants of wood, which in places leads to uranium and vanadium mineralization. The mineral forms up to 0.25 mm long, needle-like crystals or 0.5 × 1.5 mm large, short prismatic crystals with basal end faces. The crystals are typically arranged in radially fibrous groups of around 5 mm in diameter, with massive coatings of 1.5 × 2.5 cm in size.
physical and chemical properties
The crystals of Dickthomssenite are light golden brown, while their line color is always white. The surfaces of the translucent crystals show a characteristic glass-like sheen . Dickthomssenite has a medium-high refraction (n α = 1.6124; n β = 1.6740; n γ = 1.7104) and a very high birefringence (δ = 0.0980) corresponding to this glass gloss . The latter is one of the highest birefringence that has been measured on biaxial minerals.
Dickthomssenite shows a very perfect cleavage after {100}, but due to its brittleness it breaks like solid gold , whereby the fracture surfaces are hooked.
The mineral has a Mohs hardness of 2.5 and is one of the soft minerals that can be scratched with a fingernail or calcite (hardness 3) with a copper coin, just like the reference minerals plaster of paris (hardness 2) . The measured density for Dickthomssenite is> 1.96 g / cm³ and <2.09 g / cm³ (measured), the calculated density is 2.037 g / cm³.
Dickthomssenite crystals do not fluoresce in either short-wave or long-wave UV light . Under the electron beam, the mineral shows rapid dehydration. There is no information on the behavior of the mineral in front of the soldering tube or in relation to acids and alkalis .
Education and Locations
As a very rare mineral formation, Dickthomssenite has so far (as of 2019) only been described by six sites. The type locality for Dickthomssenite is the uranium-vanadium deposit "Firefly-Pigmay", which has been idle since 1956 and is located 16 km east of La Sal in San Juan County in Utah , USA . It is the oxidation zone of a sandstone-based UV deposit of the "Colorado Plateau" type.
Dickthomssenite was identified by its type locality in the form of encrustations on sandstone. The formation of the mineral apparently only took place after mining activities had ceased as a result of the action of circulating groundwater, as was similarly described for the formation of the pascoite . In the La Sal area, UV minerals are restricted to certain layers in the sandstone (paleochannels). In most cases, the ore bodies are bound to calcareous material, which may represent a reducing environment for the vanadyl and uranyl ions contained in solutions . In the “Firefly-Pigmay Mine” both oxidized and only partially oxidized UV minerals occur. In the region of the upper workings are mainly carnotite and Tyuyamunit present, while not oxidized in the lower, rich in groundwater degrading the mine minerals such as uraninite , Coffinit , Corvusit and montroseite prevail.
Typical accompanying minerals of Dickthomssenits are Pascoit, Sherwoodit , solid selenium , Bariandit , Devillin , Rossit, Hewettit, carnotite, Clausthalit , Coffinit, Tyuyamunit, uraninite, Corvusit, montroseite, roscoelite , galena , pyrite and Tennantit .
In addition to the type locality, there are a few other sites for Dickthomssenite, all of which are located in genetically similar deposits in the US states of Colorado and Utah.
- the "Packrat Mine" at Gateway in the Gateway District, Mesa County , Colorado , USA
- the “Little Eva Mine” and the “Paris No. 25 Mine “at Yellow Cat Mesa, Thompsons District (SE Thomsons), Grand County , Utah, USA
- the "Vanadium Queen Mine" near La Sal in the La Sal District (Paradox Valley District), San Juan Co., Utah, USA
- the "Blue Cap Mine" in Lion Canyon, La Sal District (Paradox Valley District), San Juan Co., Utah, USA
Sites for Dickthomssenite from Germany , Austria and Switzerland are therefore unknown.
use
Dickthomssenite is only of interest to mineral collectors due to its rarity.
See also
literature
- John M. Hughes, Forrest E. Cureton, Joseph Marty, Robert A. Gault, Mickey E. Gunter, Charles F. Campana, John Rakovan, André Sommer, Matthew E. Brueseke: Dickthomssenite, Mg (V 2 O 6 ) · 7H 2 O, a new mineral species from the Firefly-Pigmay mine, Utah: descriptive mineralogy and arrangement of atoms . In: The Canadian Mineralogist . tape 39 , no. 6 , 2001, p. 1691–1700 , doi : 10.2113 / gscanmin.39.6.1691 (English, rruff.info [PDF; 3.9 MB ; accessed on February 20, 2019]).
- Joseph A. Mandarino: New minerals . In: The Canadian Mineralogist . tape 40 , no. 4 , 2002, p. 1215–1234 , doi : 10.2113 / gscanmin.40.4.1215 (English, rruff.info [PDF; 145 kB ; accessed on February 20, 2019]).
- Thick homssenite . 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; 71 kB ; accessed on February 20, 2019]).
Web links
- Mineral Atlas: Dickthomssenite (Wiki)
- Thick homssenite. In: mindat.org. Hudson Institute of Mineralogy, accessed February 20, 2019 .
- David Barthelmy: Dickthomssenite Mineral Data. In: webmineral.com. Retrieved February 20, 2019 .
- Dickthomssenite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on February 20, 2019 .
- American-Mineralogist-Crystal-Structure-Database - Dickthomssenite. In: rruff.geo.arizona.edu. Retrieved February 20, 2019 .
Individual evidence
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap John M. Hughes, Forrest E Cureton, Joseph Marty, Robert A. Gault, Mickey E. Gunter, Charles F. Campana, John Rakovan, André Sommer, Matthew E. Brueseke: Dickthomssenite, Mg (V 2 O 6 ) 7H 2 O, a new mineral species from the Firefly-Pigmay mine, Utah: descriptive mineralogy and arrangement of atoms . In: The Canadian Mineralogist . tape 39 , no. 6 , 2001, p. 1691–1700 , doi : 10.2113 / gscanmin.39.6.1691 (English, rruff.info [PDF; 3.9 MB ; accessed on February 20, 2019]).
- ^ IMA / CNMNC List of Mineral Names; November 2018 (PDF 1.65 MB)
- ↑ Dickthomssenite . 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; 71 kB ; accessed on February 20, 2019]).
- ↑ a b c Dickthomssenite. In: mindat.org. Hudson Institute of Mineralogy, accessed February 20, 2019 .
- ↑ a b Dickthomssenite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on February 20, 2019 .
- ↑ Localities for Dickthomssenite. In: mindat.org. Hudson Institute of Mineralogy, accessed February 20, 2019 .
- ↑ Find location list for Dickthomssenite at the Mineralienatlas and at Mindat (accessed on February 20, 2019)
- ↑ Anthony Kampf, Barbara P. Nash, Joe Marty, John M. Hughes: Mesaite, CaMn 2+ 5 (V 2 O 7 ) 3 12H 2 O, a new vanadate mineral from the Packrat mine, near Gateway, Mesa County, Colorado, USA . In: Mineralogical Magazine . tape 81 , no. 2 , 2017, p. 319–327 , doi : 10.1180 / minmag.2016.080.095 (English).
- ↑ Anatoly V. Kasatkin, Jakub Plášil, Joseph Marty, Atali Al Agakhanov, Dimitrii Ilyich Belakovskiy, Inna S. Lykova: Nestolaite, CaSeO 3 · H 2 O, a new mineral from the Little Eva mine, Grand County, Utah, USA . In: Mineralogical Magazine . tape 78 , no. 3 , 2014, p. 497–505 , doi : 10.1180 / minmag.2014.078.3.02 (English).
- ↑ Anthony Kampf, John M. Hughes, Joe Marty, Barbara P. Nash: Postite, Mg (H 2 O) 6 Al 2 (OH) 2 (H 2 O) 8 (V 10 O 28 ) ∙ 13 H 2 O, a new mineral species from the La Sal mining district, Utah: crystal structure and descriptive mineralogy . In: The Canadian Mineralogist . tape 50 , no. 1 , 2001, p. 45–53 , doi : 10.3749 / canmin.50.1.45 (English, rruff.info [PDF; 733 kB ; accessed on February 20, 2019]).