Scenicsit
| Scenicsit | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1993-011 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Sulphates (selenates, tellurates, chromates, molybdates and tungstates) |
|
System no. to Strunz and to Dana |
7.GB.10 ( 8th edition : VI / G.02) 48.03.05.01 |
| Similar minerals | Lindgrenite |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pnnm (No. 58) |
| Lattice parameters | a = 12.559 Å ; b = 8.518 Å; c = 6.072 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | {100}, {110}, {211}, {010} |
| Physical Properties | |
| Mohs hardness | 3.5 to 4 |
| Density (g / cm 3 ) | 4.26 (measured); 4.30 (calculated) |
| Cleavage | good according to (100) and according to (010) |
| Break ; Tenacity | not specified; brittle |
| colour | dark green |
| Line color | malachite green |
| transparency | transparent |
| shine | Diamond luster |
| Crystal optics | |
| Refractive index | n > 1.8 |
| Birefringence | δ = 0.017 |
| Optical character | biaxial positive |
| Axis angle | 2V = 74 ° |
| Pleochroism | clearly from X = yellow-green to Y = Z = green |
| Other properties | |
| Chemical behavior | potentially unstable even with weak acids and with strong alkalis |
Scenicsite is a rare mineral from the mineral class of " sulfates (including selenates , tellurates , chromates and wolframates )". It crystallizes in the orthorhombic crystal system with the composition Cu 3 (MoO 4 ) (OH) 4 , that is a copper - molybdate with four additional hydroxide .
Scenicsite mainly forms thin-tabular crystals with a maximum size of 3 cm, which have grown together to form fan-shaped aggregates , but can also be found in the form of fissures around 5 mm thick in a hydrothermally altered granite matrix .
The type locality of the scenicsite is the mine “Jardinera No. 1, which is now idle and formerly mining secondary copper ores”. 1 “( coordinates of the copper mine Jardinera No. 1 ) near Inca de Oro, Province Chañaral, Región de Atacama (Region III), Chile .
Etymology and history
In January 1993, the US Minerals dealer Terry Szenics found a green, originally in a small copper deposit in northern Chile Lindgrenit held mineral. Via the “Aurora Mineral Corporation”, Freeport, New York, the material was transferred to the Harvard Mineralogical Museum in Cambridge , Massachusetts , USA . The first X-ray diffractometric examinations already showed that this mineral was neither Lindgrenite nor any other known mineral. After intensive investigations by an American team of mineralogists and crystallographers led by the then curator of the Mineralogical-Geological Museum at Harvard University Carl A. Francis , the new mineral was presented to the International Mineralogical Association (IMA), which recognized it as a new mineral in 1993. Having already in 1994, a brief description of the new Minerals, however, was published with a completely wrong location, the first scientific description was made of this mineral as Szenicsit ( English Szenicsite ) in 1997 by Carl A. Francis, Lawrence C. Pitman and David E Long in the US magazine The Mineralogical Record , now with the correct location. The authors named the new mineral after the finders, Zoltan Terry Szenics (* 1947) and Marissa Szenics (* 1950).
The type material for scenicsite (cotypes) is stored under catalog numbers 133734-133735 and 133738-133739 in the collection of the Mineralogical & Geological Museum at Harvard University in Cambridge, Massachusetts, USA.
In order to be able to exploit the occurrence of the new mineral alone and undisturbed, Terry Szenics had deliberately and knowingly provided false information with regard to the location and stated that the alleged location of the new mineral was "Tierra Amarilla" in Chile, about 100 km south of the actual location. In a very similar way, Giachen Fidel Caveng (1811 - 1872) from Graubünden hid the first place of discovery of the milarite he found in autumn 1868 by relocating the actual place of discovery in Val Giuv near Sedrun , Graubünden , Switzerland , to the neighboring Val Milà , which the first person described, Gustav Adolf Kenngott , to name it as "Milarit". The way in which scenics " fed the scientists with wrong data ... " sparked a discussion on the ethics of this behavior, culminating in the consideration of renaming the mineral scenicsite in order not to honor such behavior as well. Obviously, such behavior is still considered a minor offense , because in " recognition of Terry's lifelong commitment to minerals and his diligent field work discovering a great many important and beautiful mineral specimens in North and South America " Terry Szenis " was presented with the 2016 American Mineral Heritage Award at the 2016 Tucson Show "( German In recognition of Terry's lifelong commitment to minerals and his careful field work, during which he discovered many important and beautiful minerals in North and South America, he was awarded the American Mineral at the 2016 Tucson Show Heritage Award 2016 ).
classification
In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the scenicsite belonged to the mineral class of " sulfates , chromates , molybdates and tungstates (as well as some selenates and tellurates)" and there to the department of "molybdates and tungstates", where it together with Ferrimolybdit , Biehlit , Cuprotungstit , Lindgrenit and Vergasovait the "Lindgrenit-Ferrimolybdit group" with the system number. VI / G.02 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 the scenicsite to the class of "sulfates (selenates, tellurates, chromates, molybdates and wolframates)" and also to the department of "Molybdates and Wolframates". However, this is further subdivided according to the possible presence of additional anions and / or water of crystallization , so that the mineral can be found according to its composition in the subsection "With additional anions and / or H 2 O", where it is the only member of the unnamed group 7 .GB.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the scenicsite, however, to the class of "phosphates, arsenates and vanadates", but also to the department of "molybdates and tungstates". Here he is the only member of the unnamed group 48.03.05 within the sub-section " Anhydrous molybdates and wolframates (basic and anhydrous) ".
Chemism
Twenty microprobe analyzes on scenicsite from the type locality resulted in mean values of 0.14% Al 2 O 3 ; 56.25% CuO; 34.00% MoO 3 and 8.79% H 2 O (total 99.19%). On the basis of eight oxygen atoms , the empirical formula Cu 2.97 Al 0.01 (MoO4) 0.99 (OH) 4.09 was calculated, which was idealized to Cu 3 (MoO 4 ) (OH) 4 . This ideal formula requires contents of 57.01% CuO; 34.38% MoO 3 and 8.61% H 2 O.
Scenicsite is the more hydroxyl-rich analogue of lindgrenite, which is lower in hydroxyl, Cu 3 (MoO 4 ) (OH) 2 . Its monoclinic dimorph Markascherite is chemically identical to scenicsite . Chemically similar is Huenit , Cu 4 (MoO 4 ) 3 (OH) 2 .
Crystal structure
Scenicsite crystallizes in the orthorhombic crystal system in the space group Pnnm (space group no. 58) with the lattice parameters a = 12.559 Å ; b = 8.518 Å and c = 6.072 Å as well as four formula units per unit cell .
The crystal structure of the Szenicsits is made parallel to the c-axis [001] extending three chains of copper octahedra , by MoO 4 2- - tetrahedra are connected to a skeleton (refer to the right figure).
There are three Cu 2+ positions in the scenicsite (Cu2, Cu3 and Cu4), each surrounded by six oxygen atoms in a distorted octahedral configuration with four short and two longer bonds, as is the case for octahedral Cu 2+ in copper oxy salts is typical due to the Jahn-Teller effect . Cu2 octahedra are linked by common edges and form a straight single chain, while the Cu3 and Cu4 octahedra are alternately connected via common edges - but also form a single octahedral chain. Each Cu3-Cu4 chain is flanked by two Cu2 chains with common edges, thereby forming an octahedral chain of three extending parallel to the c-axis. The MoO 4 2− tetrahedron connects three chains of three via common corners. The tetrahedron has two connections to form a chain of three, the connection being made via two apical oxygen atoms of neighboring Cu2 octahedra. Due to the relative size of the MoO 4 2− tetrahedron, a paired configuration of the tetrahedra, which connect two Cu2 octahedra of the same chain of three, is possible without major distortion of the chain of three.
Furthermore, the paired configuration enables a twofold axis of rotation (Digyre) parallel to the c-axis. This leads to a staggered arrangement of those tetrahedra that have only one corner in common with the chain of three, and is responsible for the distinction between Cu3 and Cu4 octahedra, which have either two or no corners in common with the MoO 4 2− tetrahedra . The arrangement of the long axes of the distorted octahedron has a honeycomb-like appearance corresponding to the twofold axis of rotation parallel to the c-axis.
The crystal structure of scenicsite is closely related to that of antlerite , Cu 3 SO 4 (OH) 4 , which contains similar triple chains of Cu 2+ Φ 6 octahedra linked by common edges .
properties
morphology
Scenicsite mainly forms thin tabular to leafy, free-standing crystals with a maximum size of 3 cm, which have also grown in cavities and which are typically stretched along the c-axis [001] (compare the crystal drawings opposite). The crystals of this habitus 1 are tabular or leafy according to {100} and almost always have jagged edges. The dominant form, which determines the costume, is the pinacoid {100}. The crystals form radial aggregates similar to the pages of an open book and often have shiny, bent {010} cleavage surfaces. Crystals with limited end faces are very rare. Leafy crystals (habit 2) parallel to the b-axis [010] were found very rarely, while some loose crystals consist of the dipyramid {211} which determines the costume and which are only terminated by the surfaces of the pinacoid {010] (habit 3).
- Costume and habitus of scenicsite crystals (the same colors mean the same surface shapes)
1. Habit 1: leaved
2. Habit 2: leaved
3. Habit 3: blocky
4. leaved
5. leaved
5. blocky
The crystal forms {100}, {110}, {211} and {010} in the list given by Carl Francis and co-workers change to {010} in the list chosen by Jano Stolz and Thomas Armbruster, in which a and b were swapped }, {110}, {121} and {100} (compare the crystal drawings opposite).
In addition to being in the form of crystals, scenicsite also occurs as a gap filling approx. 5 mm thick in a hydrothermally modified granite matrix.
physical and chemical properties
Scenicsite crystals are dark green and resemble torbernite from the Shinkolobwe mine near the former Shinkolobwe settlement, Kambove district , Haut-Katanga , Democratic Republic of the Congo . Their line color is given as "malachite green". The surfaces of the transparent crystals show a diamond-like sheen . In accordance with its strong gloss, scenicsit has a very high refraction (n> 1.8) and low to moderate birefringence (δ = 0.017). In the first description, values were given for the refraction of light (n α = 1.886; n β = 1.892 and n γ = 1.903), but the refractive indices are too high to be measured with normal immersion liquids and possibly much larger than n = 1.8. In transmitted light, the mineral is green and shows a clear pleochroism from X = yellow-green to Y = Z = green.
Scenicsit has two different, each good cleavages : according to (100) and according to (010). Scenicsit is brittle, no break is indicated. The mineral has a Mohs hardness of 3.5 to 4 and is one of the medium-hard minerals that can be easily scratched with a pocket knife, just as easily as the reference mineral fluorite (hardness 4). The measured density for szenicsite is 4.26 g / cm³, the calculated density for the ideal composition 4.30 g / cm³, for the empirically determined formula 4.28 g / cm³. Szenicsit is neither in the long term nor in the short wavelength UV light , a fluorescent .
Scenicsit is already potentially unstable with weak acids such as citric acid or acetic acid as well as with strong alkalis and should therefore not be treated with sodium dithionite or ethylenediaminetetraacetic acid (EDTA).
Education and Locations
Scenicsite is a typical secondary mineral that was formed in an arid copper-molybdenum deposit during the oxidation of primary ore minerals under arid conditions. During the hydrothermal transformation of the granitic side rock of the Cu-Mo mineralization, the feldspars were completely converted into kaolinite . Copper was used in the weathering of chalcopyrite and / or chalcocite and the molybdenum by the hydrothermal reaction of the molybdenite 2 H as molybdate - anion released. In the presence of calcium , which was available due to the decomposition of the plagioclase , powellite was formed . As a result of the copper content of the solutions containing molybdate, the powellite z. Sometimes clearly green in color, but more important is the possible precipitation of the copper molybdate scenicsite. Lindgrenite was found in seams in a zone around the scenicsite. Brochantite is the most important secondary copper ore mineral and was also formed during the oxidation of the primary copper sulfides. Brochantite and hematite form a colorful, blue-green-red spotted rock, in which the scenicsite was found in the cavities in which the molybdenite was previously located. The close association of powellite and scenicsite with molybdenite and its pseudomorphoses suggests that the dissolved molybdate ions are not particularly mobile.
Some of the former molybdenite crystals, which were up to 2 cm in size, were pseudomorphically transformed into powellite; Powellite also formed massively in the form of thin ducts and in drusen in small crystals. In addition to powellite, which is the most important accompanying mineral of the scenicsite, and the ore minerals already mentioned, the scenicsite is also accompanied by chrysocolla , brochantite, lindgrenite , solid gold , hematite, barite and quartz .
As a very rare mineral formation, the scenicsite could only be described from two sites so far (status 2019). The type locality for scenicsite is the mine “Jardinera No. 1, which is now idle and formerly mining secondary copper ores”. 1 ”, which is 5 km east of the settlement Inca de Oro and 80 km north of Copiapo in the province of Chañaral, Región de Atacama (Region III), Chile .
At first scenicsite was only found on an ore heap on the surface of the day; the site was later localized in an area measuring only 1 × 1 × 2 meters on the 60 m level. However, Georg Gebhard states that the mining of the “Jardinera No. 1 “are only 15 m deep, which contradicts the depth information in the type publication. Despite many efforts, no other Scenicsite leading areas have been discovered in this mine. It is estimated that the amount of scenicsite extracted is only two to three kilograms.
The only other site for scenicsite is the Cu-Ag deposit of the “Carlota Mine” (also “Cactus Deposit”, “Brewery Mine” or “Alexander Mine”) at Top of the World, which was discovered in 1900 and was in production from 1929 to 1964 on Pinto Creek, Miami-Inspiration District, Globe - Miami -District, Gila County , Arizona , USA . Scenicsite typically occurs here together with azurite , powellite and prosopite .
Sites for scenicsit from Germany , Austria and Switzerland are therefore unknown.
use
Scenicsite would be a rich Cu-Mo ore due to its contents of 57.01% CuO and 34.38% MoO 3 . Due to its extreme rarity, it is only of interest to mineral collectors.
See also
literature
- Carl A. Francis, Lawrence C. Pitman, David E. Lange: Szenicsite, a new mineral from Tierra Amarilla, Chile . In: The Mineralogical Record . tape 25 , no. 1 , 1994, p. 76 (English, rruff.info [PDF; 1.4 MB ; accessed on January 15, 2019]).
- Carl A. Francis, Lawrence C. Pitman, David E. Lange: Szenicsite, a new copper molybdate from Inca de Oro, Atacama, Chile . In: The Mineralogical Record . tape 28 , no. 5 , 1997, pp. 387-394 (English).
- Scenic site . 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; 66 kB ; accessed on January 15, 2019]).
Web links
- Mineral Atlas: Scenicsite (Wiki)
- Mindat - Scenicsite (English)
- Webmineral - Scenicsite (English)
- RRUFF - Scenic site (English)
- American-Mineralogist-Crystal-Structure-Database - Scenicsite (English)
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 Carl A. Francis, Lawrence C. Pitman , David E. Lange: Szenicsite, a new copper molybdate from Inca de Oro, Atacama, Chile . In: The Mineralogical Record . tape 28 , no. 5 , 1997, pp. 387-394 (English).
- ^ IMA / CNMNC List of Mineral Names; November 2018 (PDF 1.65 MB)
- ^ 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. 420 .
- ↑ a b c d e f Jano Stolz, Thomas Armbruster: X-ray single-crystal structure refinement of szenicsite, Cu 3 MoO 4 (OH) 4 , and its relation to the structure of antlerite, Cu 3 SO 4 (OH) 4 . In: New yearbook for mineralogy, monthly books . tape 1998 , no. 6 , 1998, pp. 278-288 (English).
- ↑ a b Rupert Hochleitner, Stefan Weiß: Scenicsit profile . In: Lapis . tape 40 , no. 4 , 2015, p. 7-9 .
- ^ A b c Carl A. Francis, Lawrence C. Pitman, David E. Lange: Szenicsite, a new mineral from Tierra Amarilla, Chile . In: The Mineralogical Record . tape 25 , no. 1 , 1994, p. 76 (English, rruff.info [PDF; 1.4 MB ; accessed on January 15, 2019]).
- ^ Gustav Adolf Kenngott : Communication to Professor G. Leonhard from September 30, 1869 . In: New Yearbook for Mineralogy, Geology and Paleaontology . tape 1870 , 1870, pp. 80–81 ( rruff.info [PDF; 245 kB ; accessed on January 15, 2019]).
- ↑ a b c Georg Gebhard: The story of the scenicsite and Christelite . In: Lapis . tape 24 , no. 1 , 1999, p. 42-44 .
- ↑ Wendell E. Wilson (2019): Terry Szenics - Mineralogical Record Biographical Archive, at www.mineralogicalrecord.com , accessed on January 15, 2019 (English)
- ↑ a b c d Mindat - Szenicsite , accessed on January 15, 2019 (English)
- ↑ Peter C. Burns: The crystal structure of szenicsite, Cu 3 MoO 4 (OH) 4 . In: Mineralogical Magazine . tape 62 , no. 4 , 1998, pp. 461–469 , doi : 10.1180 / 002646198547837 (English, rruff.info [PDF; 451 kB ; accessed on January 15, 2019]).
- ↑ a b c Mineralienatlas - Szenicsit , accessed on January 15, 2019
- ↑ Mindat - number of locations for Szenicsit , accessed on January 15, 2019 (English)
- ↑ List of localities forcenicsite in the Mineralienatlas and Mindat (accessed on January 15, 2019)
- ↑ Scenic site . 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; 66 kB ; accessed on January 15, 2019]).
- ↑ RRUFF - Szenicsite, Locality: Carlota mine, Pinto Creek, Gila, Arizona, USA , accessed on January 15, 2019 (English)