Pyrostilpnit

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Pyrostilpnit
Pyrostilpnite-217330.jpg
Pyrostilpnite in typical fan-shaped aggregates from St. Andreasberg, Harz, Lower Saxony (field of view approx. 2.5 mm)
General and classification
other names
  • noble fire screen
  • diatom fire screen
  • Fireblende
  • Pyrichrolites
  • Pyrochrotite
  • Pyrichrotites antimoneus
chemical formula Ag 3 [SbS 3 ]
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.GA.10 ( 8th edition : II / E.07)
04/03/02/02
Similar minerals Proustite, pyrargyrite, xanthocone, samsonite, quadratite
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / c (No. 14)Template: room group / 14
Lattice parameters a  = 6.84  Å ; b  = 15.84 Å; c  = 6.24 Å
β  = 117.1 °
Formula units Z  = 4
Frequent crystal faces {010}, {210}, {141}, { 1 41}, {111}, {101}, { 1 01}
Twinning according to {100} with (100) as the twin plane and [001] as the twin axis
Physical Properties
Mohs hardness 2 to 2.5; VHN 100g = 95–115 kg / mm², (mean 107)
Density (g / cm 3 ) 5.94 (measured); 5.97 (calculated)
Cleavage completely after (010)
Break ; Tenacity clamshell; somewhat flexible in thin plates (flexible)
colour hyacinth red to brownish red, orange red and flame red, always lighter than pyrargyrite; lemon yellow in transmitted light
Line color yellow-orange
transparency transparent
shine Diamond-like pearlescent luster, diamond luster
Crystal optics
Refractive indices n α  = extremely high
n β  = extremely high
n γ  = extremely high
Birefringence δ = extremely high
Optical character biaxial positive
Other properties
Chemical behavior decomposed by hydrochloric acid with separation of sulfur and Sb 2 O 3
Special features photosensitive, the surface becomes darker when exposed to light

Pyrostilpnit is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts " with the chemical formula Ag 3 [SbS 3 ]. From a chemical point of view, this makes the mineral a silver - sulfoantimonide .

Pyrostilpnite crystallizes in the monoclinic crystal system and develops up to 1 mm (in exceptional cases up to 10 mm) long, after {010} tabular and elongated parallel [001] ledge-shaped crystals . Sub-parallel intergrowth results in fan-shaped to cluster-shaped aggregates with extremely high refraction , double refraction and a strong diamond luster.

Etymology and history

In the third year of the “Yearbook for the Miner and Hüttenmann” published by the “Königliche Bergacademie zu Freyberg” and first published in 1827, an anonymous author explains:

“On the seventh Gezeug route at Churprinz Friedrich August Erbst. has, however, as a rarity, and on New Hope God's inheritance. At Bräunsdorf only traces of a new hyacinth-red silver ore broken into thin crystals resembling women's ice, the main components of which are sulfur silver and sulfur antimony, which, according to its external characteristics, stands between red spit gloss ore and red gold ore, and which Professor Breithaupt called the systematic name diatomic fire screen is. "

The discoverer of the pyrostilpnite is therefore the famous Freiberg mineralogist August Breithaupt , which makes this mineral one of his 40 first mineral descriptions. Interestingly enough, the first mention of the name "fire screen" dates back to 1829. Breithaupt described this new mineral in 1832 "from the Prince Elector at Freiberg" and called it "noble fire screen". He did not give reasons for choosing the name, but the high silver content of almost 60% and the dazzle-like diamond luster may have been the inspiration for the name. The full name of the type locality is "Churprinz Friedrich August Erbstolln", Großschirma near Freiberg.

The name still used today, Pyrostilpnit, comes from James Dwight Dana . At first he only incompletely translated Breithaupt's term “Fireblende” into English, but later chose a different language and named the mineral after the Greek words πῦς [ pyr ] and στιλπνὀς [ stilpnos ] for “fire” and “shine” - put together “dem Fire alike ”with regard to color and luster.

The type material of the mineral is kept in the mineralogical collection of the Technical University Bergakademie Freiberg under the catalog numbers 6200 (holotype) and 6205 (probably part of the holotype) at the locations G 5.5 and G 5.6.

classification

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Pyrostilpnit belonged to the mineral class of "sulfides and sulfosalts" and there to the general ward of the "thio" where he along with Proustite , Pyrargyrite , Quadratit , Samsonit and Xanthokon the unnamed group II / E.07 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 pyrostilpnite to the class of “sulfides and sulfosalts”, but in the newly defined section of “sulfoarsenides, sulfoantimonides, sulfobismuthides” ", a. This department is further subdivided according to the crystal structure and the possible presence of further sulfur, so that the mineral according to its structure and its composition in the subdivision of "island sulfarsenides (Neso sulfarsenides) etc., without additional sulfur (S)" can be found where it only forms the unnamed group 2.GA.10 together with xanthocone .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , sorts pyrostilpnite into the class of "sulfides and sulfosalts" and there in the department of "sulfosalts". Here it is within the subsection “ Sulphosalts with the ratio 3> z / y and the composition (A + ) i (A 2+ ) j [B y C z ], A = metals, B = semimetals, C = non-metals ” find where, together with xanthocones, he creates the "xanthocone group" with system no. 04/03/02 forms.

Crystal structure

Pyrostilpnite crystallizes in the monoclinic crystal system in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 6.84  Å ; b  = 15.84 Å; c  = 6.24 Å and β = 117.1 ° as well as four formula units per unit cell . Template: room group / 14

The structural units of the crystal structure of the pyrostilpnite are Sb-S pyramids , Ag-S chains and Ag-S networks, which are linked to one another via common sulfur atoms. The Sb atoms form a trigonal SbS 3 pyramid with three S atoms in such a way that the Sb atoms are at the tips of the pyramids, while the base is formed by the three sulfur atoms. Ag atoms in the Ag-S chains also have five closest Ag neighbors at a distance of 3.03–3.15 Å. The sulfur atoms form deformed pseudo-hexagonal densely packed layers parallel (010). Overall, the structure of the pyrostyle pnite can be interpreted as a superposition of four closely packed pseudo-hexagonal nets, which are superimposed so that the coordination number 10 arises.

Modifications and varieties

Pyrostilpnite is the second modification of the compound Ag 3 [SbS 3 ] besides pyrargyrite . It represents the monoclinic dimorph to the trigonal pyrargyrite and, at the same time, its low-temperature modification. Pyrargyrite and pyrostilpnite are thus polymorphs whose inversion temperature is below 197 ° C, whereby this inversion takes place without the formation of further phases. It has long been known that pyrostilpnite is only resistant below 192 ± 5 ° C. In more recent work, the transformation temperature was determined to be 465 K (= 191.85 ° C) and an enthalpy D R H of 40.32 kJ / mol was determined. This is considerably larger than z. B. with similar silver sulfosalt pairs such as trechmannite and smithite, which is attributed to the fact that the structural differences between pyrostilpnite and pyrargyrite are greater than those between trechmannite and smithite, which means that larger transformation enthalpies are required.

Irrespective of the low inversion temperature, pyrargyrite can only be synthesized from its elements at temperatures> 350 ° C. Attempts to synthesize pyrostilpnite, however, have so far been unsuccessful, possibly due to the low temperature range of its stability. The lowest temperatures at which reactions take place in this system are already in the stability field of the pyrargyrite. The melting point for Ag 3 SbS 3 (pyrargyrite) is 485 ° C. The existence of a complete mixed crystal formation between prostite and pyrargyrite is out of the question at least at high temperatures and at least partially takes place at low temperatures. Recent studies indicate that Proustite-Pyrargyrite mixed crystals re-equilibrate when cooling and separate into phases with almost the final link composition. Examples of an intermediate composition of pyrargyrite-prostite mixed crystals are rare in nature. They must have been created by cooling above the solvus. A mixed crystal formation for pyrargyrite and pyrostilpnite, however, can be excluded due to the different space groups of both minerals. However, regular adhesions of pyrostilpnite and xanthocone have been described.

properties

morphology

Pyrostilpnite forms 1–2 mm long, thin tabular crystals according to {010} and parallel [001] elongated crystals. On the pinacoid {010} stripes parallel [10 1 ] and sometimes also parallel [101] can often be seen.

The most important surface shapes are {010}, {210}, {141}, { 1 41}, {111}, {101}, { 1 01}, although mostly only the pinacoid {010} shows clear surfaces. All other shapes show only small, narrow areas in zone [001] and the geometrically equivalent zones [10 1 ] and [101]. These are mostly crystals with a greater area, whereas also crystals with little area, e.g. B. only {010}, {111} and {11 1 } exist.

Sub-parallel growth leads to cluster, fan and tree-shaped aggregates. Breithaupt had already compared these aggregates with "curved crystals" similar to those of desmin ( stilbit ) due to their very similar design . Twins according to {100} with (100) as the twin plane and [001] as the twin axis are common. The formation of twins results in the pseudo-orthorhombic appearance of the crystals.

Occasionally larger crystals are also recovered. The largest known pyrostilpnite crystal comes from the Andreaskreuzer Gang near St. Andreasberg and is 10 mm long and 4 mm wide.

Physical Properties

The crystals of pyrostilpnite are bright hyacinth red or brownish red, orange red and fire red, but always lighter than pyrargyrite. The streak color of the mineral is described as yellow-orange. The transparent crystals have a pronounced diamond-like sheen , which is also reflected in an extremely high refraction of light and double refraction . Numerical values ​​for "both not yet known exactly". On the other hand, pyrostilpnite shows a pearlescent sheen on the surfaces of the pinacoids {010}. According to (010), the mineral shows perfect cleavage and shell-like breakage , but is somewhat pliable (flexible) in thin platelets. With a Mohs hardness of 2 to a maximum of 2.5, pyrostilpnite is one of the soft minerals that, like the reference mineral gypsum (hardness 2), can be scratched with the fingernail. The calculated density is 5.97 g / cm³.

In reflected light (bevel), pyrostilpnite is gray and significantly less blue than pyrargyrite. The reflectivity is approx. 25%. The reflection pleochroism is smaller than with pyrargyrite and only visible in oil at the grain boundaries. The same applies to the anisotropy effects, which are difficult to see due to the internal reflections. The inner reflexes are yellow to yellow-brown and orange-brown, but almost never red.

Pyrostilpnite is - similar to Proustit and Pyrargyrite - photosensitive and becomes darker on the surface when exposed to light. It is therefore advisable not to expose the mineral to sunlight if possible and to store it protected from light.

Chemical properties

From a chemical point of view, pyrostilpnite shows a behavior comparable to that of pyrargyrite. This can be melted into a ball in front of the soldering tube on carbon by spraying, and the carbon is fogged with Sb 2 O 3 . After prolonged heating in the oxidation flame or with soda in the reduction flame, the ball gives a grain of silver. In an open tube sulphurous vapors and a white sublimate of Sb 2 O 3 ; in the flask a red sublimate of antimony oxysulphide. When melting with ammonium nitrate, gives a solution of silver sulfate and a residue of Sb 2 O 3 + Sb 2 O 5 . Decomposed by hydrochloric acid with separation of sulfur and Sb 2 O 3 . Colored black by potassium hydroxide solution when heated; Hydrochloric acid then precipitates orange-colored flakes of sulfur antimony from the lye.

Education and Locations

Pyrostilpnit formed by hydrothermal processes in low-temperature silver - and antimony-containing veins, where he in paragenesis especially with Pyrargyrite, but also stephanite, Akanthit, silver, Miargyrit, Xanthokon, Andorit and Fizelyit and the gaits found quartz and calcite.

In his "Paragenesis of Minerals", Breithaupt gives successions (age consequences) of the minerals occurring with pyrostilpnite. Translated into today's nomenclature, the sequence (from oldest to youngest mineral) is as follows:

  • Mine “New Hope God”, Bräunsdorf near Freiberg: 1) quartz, 2) pyrargyrite, 3) pyrostilpnite
  • Freiberg Revier: 1) quartz, 2) pyrargyrite, 3) pyrostilpnite, 4) quartz ("ordinary" without the second quartz)
  • St. Andreasberg district: 1) older calcite, 2) solid arsenic, 3) calcite, 4) solid arsenic, 5) galena, 6) "hypargyrite" (miargyrite?) 7) pyrostilpnite (e.g. from the "Samsoner Hauptgang") )
  • St. Andreasberg district: 1) quartz, 2) pyrostilpnite

According to the low transformation temperature in pyrargyrite, pyrostilpnite is often one of the youngest or the youngest formation at all. B. on the steps of St. Andreasberg on pyrargyrite, dignified arsenic, calcite, galena, quartz or even directly on the adjacent rock (slate).

Pyrostilpnite has only been described as a rare mineral formation from a few localities, although it occurs relatively frequently in its paragenesis in small quantities among the most recent formations. So far (as of 2016) around 90 sites are known. The type locality is the “Churprinz Friedrich August Erbstolln”, large umbrella company near Freiberg , Erzgebirge , Saxony .

Pyrostilpnite crystal approx. 5.5 mm long from St. Andreasberg, Harz, Lower Saxony

In addition to its type of locality, pyrostilpnite was also found in Germany in the pits "United Field" and " Himmelsfürst ", Brand-Erbisdorf , "Beschert Glück" near Zug , "New Hope God", Bräunsdorf , " Himmelfahrt " near Freiberg, "Blessing God" near Gersdorf , "Sauberg" near Ehrenfriedersdorf and on the "Katharina Flachen" in the " Fundgrube Türk ", Schneeberg , all in the Ore Mountains. Magnificent crystals come from various pits such as “ Samson ”, “ God's grace ”, “Franz-August”, “Bergmannstrost”, “Theuerdank”, “St. Andreaskreuz ”,“ Jacobsglück ”and“ Claus-Friedrich ”, all in the St. Andreasberg district , Lower Saxony , Harz . Also from the “ Fischbacher Werk ”, Niederfischbach , Rhineland-Palatinate , and “ Grube Brüderbund ”, Eiserfeld , North Rhine-Westphalia , both in Siegerland . Finally from the " Grube Clara " in Rankachtal and the "Wenzel" mine in Frohbachtal near Oberwolfach as well as the "Tannenboden" mines near Wieden , "Teufelsgrund" at Belchen , "Ludwig" near Hausach and "Hornbühl" near Waldkirch , all in the Black Forest , Baden-Württemberg .

From the arsenic mine at Lower Rotgüldensee, Rotgülden, Murwinkel, Lungau , Salzburg , Austria . Locations in Switzerland are not known.

From the “Anna” mine, Březové Hory deposit, and from the “uranium mine No. 7 “near Třebsko, Příbram , Central Bohemian Region , Czech Republic , as well as from the mines of Banská Štiavnica (Schemnitz), Okres Banská Bystrica , Slovakia . From Hiendelaencina, Guadalajara (here on Freielebenit), Castile-La Mancha , Spain , and from St Teath , Cornwall , England , United Kingdom .

From the "Van Silver Mine" (Silver Tunnel) at Whistler in the Vancouver Mining Division, from the "Silvana Mine" at Sandon, both British Columbia , and from Cobalt , Ontario , all in Canada . In the United States from the Silver City District, Owyhee County , Idaho ; from the Bulldog Mine and the Wagon Wheel Gap Mine, Creede Quadrangle, Mineral Co. , Colorado ; as well as from the "Kelly Mine" near Randsburg and the "Coyote Mine", both in San Bernardino County , California . From "Cerro de Potosí" (Cerro Rico) near Potosí and Colquechaca (Aullagas), Chayanta province and from Tatasí, all Potosí Department , Bolivia . From the mines of Chañarcillo south of Copiapó, Copiapó Province , Región de Atacama , Chile .

From the “Kushikino Mine”, Kagoshima Prefecture , Japan and the “Mongon Tolgoi Mine”, Horqin Right Middle Banner, Hinggan , Inner Mongolia , China .

In Australia from Broken Hill , New South Wales and from the "Long Tunnel Mine", Heazlewood District, Tasmania .

Other sites are in Australia, Bulgaria , the Czech Republic, France , Greece , Hungary , Italy , Kosovo , Mexico , Morocco , Russia and the United States.

use

With an Ag content of just under 60% by weight, pyrostilpnite is a rich silver ore and has been smelted together with other silver ores in the past. However, due to its extreme rarity, the mineral is much more interesting for collectors. Otto Luedecke refers to a pyrostilpnite crystal of 5 mm in diameter from the Jacobsglücker Gang near St. Andreasberg, in the collection of the Clausthal Mining Academy at that time, for which the downright monstrous price of 1,000 marks at that time (1882) is said to have been offered.

See also

literature

  • Pyrostilpnite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF, 62 kB )
  • A. Kutoglu (1968): The structure of pyrostilpnite (fire screen) Ag 3 SbS 3 . In: New Yearbook Mineralogie Monatshefte , Volume 1968, pp. 145–160.
  • Martin Alfred Peacock (1950): Studies of mineral sulphosalts: XV. Xanthoconite and pyrostilpnite In: Mineralogical Magazine , Volume 29, pp. 346-358.
  • Otto Luedecke (1882): XXXIV. About the fire screen of St. Andreasberg. In: Zeitschrift für Krystallographie und Mineralogie , Volume 6, pp. 570-579 ( PDF, 535 kB) .

Web links

Commons : Pyrostilpnite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e f g August Breithaupt : Complete characteristics of the mineral system . 3. Edition. Arnoldische Buchhandlung, Dresden and Leipzig 1832, p.  285 and 333 ( available online in Complete Characteristics of the Mineral System , p. 285 ff. In the Google book search).
  2. ↑ a b Anonymous: Mineralogical new experiences and incidents in 1827 . In: Yearbook for the miner and smelter for the year 1829 . tape 1829 . Gerlachische Buchdruckerey, Freyberg 1829, p. 151–154 ( available online in the yearbook for the mountain and huts man for the year 1829 , p. 152 ff. In the Google book search).
  3. ^ A b James Dwight Dana : A system of mineralogy comprising the most recent discoveries . 3. Edition. George P. Putnam, New York and London 1850, p.  543 ( available online in A system of mineralogy comprising the most recent discoveries , p. 543 ff. In the Google book search).
  4. ^ Gilbert Joseph Adam: Tableau Mineralogique . 1st edition. Dunod, Paris 1869, p. 60 .
  5. ^ August Frenzel : Mineralogical Lexicon for the Kingdom of Saxony . 1st edition. Verlag von Wilhelm Engelmann, Leipzig 1817, p.  252-253 ( available online in Mineralogical Lexicon for the Kingdom of Saxony. , P. 252 f. In the Google book search).
  6. ↑ a b August Breithaupt : The Paragenesis of Minerals. Illuminated mineralogically, geognostically and chemically, with special consideration for mining . 1st edition. JG Engelhardt, Freiberg 1849, p.  152, 251, 253 and 255 ( available online in Die Paragenesis der Mineralien , p. 152 in the Google book search).
  7. ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagsbuchhandlung Nägele u. Obermiller, Stuttgart 2001, ISBN 3-510-65188-X , p.  119 .
  8. ↑ a b c Bernhard Pracejus: The ore minerals under the microscope, An optical guide . 2nd Edition. Elsevier, Amsterdam 2015, ISBN 978-0-444-62725-4 , pp. 568-569 .
  9. ↑ a b c d e Martin Alfred Peacock (1950): Studies of mineral sulphosalts: XV. Xanthoconite and pyrostilpnite. In: Mineralogical Magazine , Volume 29, pp. 346-358.
  10. ↑ a b c d e f g h i j Pyrostilpnite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 62 kB )
  11. ↑ Mindat - Pyrostilpnite
  12. ↑ a b c d Paul Ramdohr : The ore minerals and their adhesions . 4th edition. Akademie-Verlag, Berlin 1975, p.  846-847 .
  13. ↑ a b c d Carl Hintze : Handbook of Mineralogy. First volume. First division . 1st edition. Verlag Veit & Co., Leipzig 1904, pp. 1075-1078. ( available online at archive.org )
  14. ↑ a b Kurt Nassau: Conserving light sensitive minerals and gems. In: Frank M. Howie (Ed.), Care and Conservation of Geological Material. Minerals, Rocks, Meteorites and Lunar finds . Routledge, London & New York 2011, ISBN 978-1-135-38514-9 , pp. 11-24.
  15. ↑ James Dwight Dana , George Jarvis Brush : A System of Mineralogy. Descriptive mineralogy, comprising the most recent discoveries . 5th edition. John Wiley & Son, New York 1869, p.  93–94 ( available online in A system of mineralogy. Descriptive mineralogy, comprising the most recent discoveries , p. 93 ff. In the Google book search).
  16. ↑ Type mineral catalog Germany - storage of the holotype level
  17. ↑ a b c Luke Li-Yu Chang (1963): Dimorphic relation in Ag 3 SbS 3 . In: American Mineralogist , Volume 48, pp. 429-432.
  18. ↑ C. William Keighin, Russell M. Honea (1969): The System Ag-Sb-S from 600 ° C to 200 ° C. In: Mineralium Deposita , Volume 4, pp. 153-171 doi: 10.1007 / BF00208050 .
  19. ↑ Birgitt Meyer, Fritz Scholz (1997): Redetermination of the transformation enthalpies of the xanthoconite - proustite, pyrostilpnite - pyrargyrite and trechmannite - smithite phase transitions. In: Physics and Chemistry of Minerals , Volume 24, pp. 50-52.
  20. ^ Gunnar Kullerud (1966): Phase relations in sulfide-type systems. In: Sydney P. Clark, JR. (Ed.), Handbook of Physical Constants (Geological Society of America Memoir 97) , pp. 323-344, New York (Geological Society of America).
  21. ↑ Priestley Toulmin (1963): Proustite-pyrargyrite solid solutions In: American Mineralogist , Volume 48, pp. 725-736.
  22. ↑ Subhabrata Ghosal, Richard O. Sack (1995): As-Sb energetics into severe tian sulfosalts. In: Geochimica et Cosmochimica Acta , vol. 59, pp. 3573-3579.
  23. ↑ Luca Bindi, Giovanni Pratesi, Paul G. Spry (2010): Crystallographic and chemical constraints on the nature of the proustite-pyrargyrite solid-solution series. In: American Mineralogist , Volume 95, pp. 1725-1729.
  24. ^ MG Dobrovolskaya, GA Annenkova, AI Zepin (1973): Regular intergrowth of minerals of the isomorphous series of xanthoconite-pyrostilpnite. In: Zapiski RMO (Proceedings of the Russian Mineralogical Society) , Volume 102 (Issue 1), pp. 93-98.
  25. ↑ a b c Otto Luedecke (1882): XXXIV. About the fire screen of St. Andreasberg. In: Zeitschrift für Krystallographie und Mineralogie , Volume 6, pp. 570-579.
  26. ↑ Mindat - Number of localities for pyrostilpnite
  27. ↑ a b c List of localities for pyrostilpnite in the Mineralienatlas and in Mindat