Hornsite

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Hornsite
Hornesite-88587.jpg
Hörnesite (white, radial rays ) from the Schwarzleograben near Leogang -Hütten, Salzburg, Austria (field of view 5 mm)
General and classification
chemical formula Mg 3 [AsO 4 ] 2 • 8H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.CE.40 ( 8th edition : VII / C.13)
03/40/06/07
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 10.26  Å ; b  = 13.44 Å; c  = 4.74 Å
β  = 104.9 °
Formula units Z  = 2
Physical Properties
Mohs hardness 1
Density (g / cm 3 ) measured: 2.57 to 2.73; calculated: 2.57
Cleavage completely after {010}, indistinct after {100}
Break ; Tenacity mild; flexible in thin sheets
colour colorless, white, through mixed crystal formation also yellow, pink, green
Line color White
transparency transparent
shine Resin luster to wax luster, pearlescent luster on split surfaces
Crystal optics
Refractive indices n α  = 1.563
n β  = 1.571
n γ  = 1.596
Birefringence δ = 0.033
Optical character biaxial positive
Axis angle 2V = 60 ° (measured and calculated)

Hörnesite is a rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates". It crystallizes in the monoclinic crystal system with the chemical composition Mg 3 [AsO 4 ] 2 · 8H 2 O, making it a hydrous magnesium - arsenate .

Hörnesite mostly develops tabular to prismatic crystals , but also occurs in the form of radial, leafy or stalky mineral aggregates . Undamaged crystal surfaces have a resin-like to wax-like sheen , while the cracked surfaces have a more mother-of-pearl shimmer . In its pure form, Hörnesite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also appear white and due to foreign admixtures due to mixed crystal formation with annabergite and erythrin it can take on a yellow, pink or green color, with the transparency decreasing accordingly.

With a Mohs hardness of 1, like the reference mineral talc, hornsite is one of the minerals with the lowest hardness that can be scratched with a fingernail.

Etymology and history

Moriz Hörnes (1815–1868)

Hörnesite was first discovered by Gustav Adolf Kenngott , who noticed the previously unknown mineral on a sample called " Talc from the Banat " in the mineralogical collection of the kk Hof Mineralien-Cabinet . The main mass of the piece consisted of large-grain, crystallized, gray to greenish-white calcite , in which, however, star-shaped, radiant parts of snow-white, pearlescent and translucent crystals had grown. After some research, Kenngott was able to determine that the mineral sample originally came from the van der Nüll collection (possibly Eduard van der Nüll's father , Jacob Friedrich) and he also succeeded in depicting some of the crystallographic and chemical properties. However, due to his appointment to Zurich, he did not have the time for a precise analysis of the composition. In 1860 he therefore handed over his preliminary report to the board of directors of the kk Hof-Mineralien-Cabinet Moriz Hörnes and left it to him and Wilhelm von Haidinger to find a suitable name for the mineral.

Karl Ritter von Hauer finally succeeded in completely analyzing the mineral and gave the almost correct composition as an oxide formula with 3MgO · AsO 5 + 8HO. Haidinger chose the name Hörnesit in memory of the long friendship between him and the director of the Hof Mineralien-Cabinet Moriz Hörnes, who has since retired.

The type locality is the porphyry copper-molybdenum deposit near Ciclova Montană (Caraș-Severin district) in the Romanian region of Banat .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Hörnesite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions ", where together with Annabergit , Arupit , Barićit , Bobierrit , Cattiit , Erythrite , Köttigit , Manganohörnesit , Pakhomovskyit , Parasymplesit and Vivianit the "Vivianitgruppe" with the system no. VII / C.13 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 Hörnesite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the phosphate, arsenate or vanadate complex to the water of crystallization contained , so that the mineral is classified in the sub-section “With only medium-sized cations; RO 4  : H 2 O ≤ 1 "is found, where it together with Annabergit, Arupit, Barićit, Erythrin, 2.5 Ferrisymplesit , Köttigit, Manganohörnesit, Pakhomovskyit, Parasymplesit and Vivianit in the" Vivianitgruppe "with the system number . 8.CE.40 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Hörnesite to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here he is also in the " Vivianite group " with the system no. 40.03.06 within the subsection "Water-containing phosphates etc., with (A 2+ ) 3 (XO 4 ) 2 × x (H 2 O)".

Crystal structure

Hörnesite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 10.26  Å ; b  = 13.44 Å; c  = 4.74 Å and β = 104.9 ° and two formula units per unit cell . Template: room group / 12

Education and Locations

White hornsite from Sainte-Marie-aux-Mines (France), exhibited in the "Musée de minéralogie de Strasbourg "

Hörnesite forms metamorphically in thermally converted limestone blocks and tuffs . As accompanying minerals may include Fluoborit , fluorite and Hydromagnesit occur.

As a rare mineral formation, Hörnesite could only be proven at a few sites, whereby around 100 sites are known worldwide. In addition to its type locality Ciclova Montană , the mineral has so far only appeared in Romania at Săcărâmb (also Sacarîmb, Sãcãrâmb, Szekerembe and formerly Nagyág) in the Hunedoara district .

In Germany, Hörnesite was found in the Duke Friedrich mine near Reinerzau , the Clara mine near Oberwolfach, the Anton mine in the Heubachtal near Wittichen , the Help of God mine in the Stammelbach valley near Schiltach and in the cobalt mine (God's blessing) near Sulzburg in Baden-Württemberg ; in a gabbro quarry near Nieder-Beerbach and in the Bodental district near Iba (Bebra) in Hesse; in the gabbro quarry (bear quarry) near Bad Harzburg and in the Oder tunnel (Odertal) near Sankt Andreasberg in Lower Saxony; in the Alexander mine near Ramsbeck , the Glanzenberg mine in the Olpe district, in several mines in the Siegen-Wittgenstein district (Eiserfeld, Eisern, Gosenbach, Müsen) and in some mines near Heiligenhaus in North Rhine-Westphalia; in various pits near Antweiler , Schutzbach , Niederfischbach , Bad Ems and Braubach in Rhineland-Palatinate; Enlightened happiness in the mine near Wernigerode in Saxony-Anhalt; can be found in the Himmlisch Heer treasure trove near Cunersdorf (Annaberg-Buchholz) , in shaft 139 (Abrahamhalde) near Lauta (Marienberg) and in several pits near Neustädtel (Schneeberg) in Saxony and in the Lichtenberg opencast mine near Ronneburg in Thuringia.

In Austria, the mineral was found in the serpentinite quarry near Griesserhof (Gulitzen) near Hirt in the Friesach - Hüttenberg district , in the Finkenstein mine on Mallestiger Mittagskogel and in a mercury pit near Glatschach and in the Geißloch ditch near Stein in the Dellach im Drautal community in Carinthia ; in several tunnels in the Schwarzleo district in the Salzburg municipality of Leogang (Zell am See); in the Kramstollen near Maukenötz , on the Geyerköpfl and on the Silberberg near Rattenberg in the municipality of Brixlegg and on the Kaiserbründl near the Gratlspitze in Tyrol.

In Switzerland, Hörnesite is so far only known from Miglieglia in the canton of Ticino and from several mines near Ayer , Saint-Luc and Vissoie in Val d'Anniviers , the Lengenbach mine in the Binntal and the Turtmanntal (Blüomatttälli, Pipjitälli) in the canton of Valais.

Other locations include Australia, Brazil, China, France, Greece, Italy, Japan, Morocco, Macedonia, Namibia, Portugal, Russia, Sweden, Spain, the Czech Republic and the United States of America (USA).

See also

literature

Web links

Commons : Hörnesite  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ a b c d e 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.  481 .
  2. ↑ a b Hörnesite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.8 kB )
  3. ↑ a b c Mindat - Hörnesite
  4. ↑ John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Erythrite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.4 kB )
  5. ^ New German Biography (NDB) - Nüll, Eduard van der
  6. ↑ Kenngott and Haidinger 1860, see literature
  7. ↑ Information and images on the type locality in the Mineralienatlas and Mindat
  8. ↑ List of localities for Hörnesite in the Mineralienatlas and Mindat