Harmotome

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Harmotome
Harmotome-211584.jpg
Harmotome crystals from the type locality Sankt Andreasberg im Hart , Lower Saxony ( overall size  8.3 cm × 4.5 cm × 3.3 cm)
General and classification
chemical formula
  • Ba 2 (Si 12 Al 4 ) O 32 · 12H 2 O
  • Ba 2 (Ca 0.5 , Na) [Al 6 Si 10 O 32 ] • 12H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates - framework silicates (tectosilicates)
System no. to Strunz
and to Dana 		9.GC.10 ( 8th edition : VIII / F.13)
77.01.03.05
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / m (No. 11)Template: room group / 11
Lattice parameters a  = 9.88  Å ; b  = 14.14 Å; c  = 8.69 Å
β  = 124.8 °
Formula units Z  = 1
Twinning mostly complex overgrown
Physical Properties
Mohs hardness 4.5 to 5
Density (g / cm 3 ) measured: 2.41 to 2.47; calculated: 2.448
Cleavage clear after {010}, indistinct after {001}
Break ; Tenacity uneven to slightly scalloped; brittle
colour colorless, white, gray, yellow, pink, brown
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.503 to 1.508
n β  = 1.505 to 1.509
n γ  = 1.508 to 1.514
Birefringence δ = 0.005 to 0.006
Optical character biaxial positive
Axis angle 2V = 43 ° (measured); 80 ° (calculated)

Harmotome , also known under the mining names Andreasbergolith or Kreuzzeolite , is a rather seldom occurring mineral from the mineral class of " silicates and germanates " with the chemical composition Ba 2 (Si 12 Al 4 ) O 32 · 12H 2 O and therefore chemically one hydrous barium - aluminosilicate . Structurally, harmotome belongs to the zeolite family, more precisely the leaf zeolites .

Harmotom crystallizes in the monoclinic crystal system and develops mostly prismatic, complex intergrown crystal twins , but also granular to massive mineral aggregates with a glass-like sheen on the surfaces. In its pure form, Harmotome is colorless and transparent. However, due to multiple refraction due to lattice defects or polycrystalline formation, it can also be translucent white and, due to foreign admixtures, take on a gray, yellow, pink, brown color.

Etymology and history

Harmotome in the eponymous twin form

The name Harmotom is made up of the Greek words

and

  • τομή / tomɛ́ː / "cut" from τέμνω / témn ɔː / "(ab- / zer) cut, break" (documented in myk. <te-me-no> / témenos / "divided (holy) piece of land" and < du-ru-to-mo> / drutómos / "wood felling"), whose roots τεμ- / τεμε- / τμη- also in Latin templum "temple" and vlt. temnō "despise" occur.

The translation of merged cuts refers to the type of typical twinning. Harmotome usually occurs in columnar twins, in which the main axes of the two individuals coincide, but the corresponding perpendicular directions cross each other, i.e. the macrodiagonal of one coincides with the brachydiagonal of the other, so that the crystals have the shape of a cross in plan. This peculiarity also led to the synonym cross zeolite .

The second synonym Andreasbergolith refers to the type locality Sankt Andreasberg in the Upper Harz, where Harmotom was first discovered in 1801. The mineral was first described by René-Just Haüy .

classification

Already in the outdated 8th edition of the mineral classification by Strunz of Harmotom belonged to the mineral class of "silicates and Germanates" and then to the Department of "framework silicates (tectosilicates)" where he collaborated with Garronit , Gismondin , Phillipsit and Yugawaralith the "Gismondin-Phillipsit -Group "with the system no. VIII / F.13 .

In the last revised and updated Lapis mineral directory by Stefan Weiß in 2018 , which, out of consideration for private collectors and institutional collections, is still based on this type of systematics by Karl Hugo Strunz , the mineral was given the system and mineral number. VIII / J.25-70 . In the "Lapis system" this also corresponds to the section "Framework silicates", where Harmotom together with Amicit , Flörkeit , Garronit-Ca , Garronit-Na , Gismondin, Gobbinsit , Martinandresit , Merlinoit , Montesommait , Phillipsit-Ca , Phillipsit-K , Phillipsit-Na and Yugawaralith form an independent but unnamed group.

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, assigns the harmotome to the already more finely subdivided section of “tectosilicates with zeolitic H 2 O; Family of zeolites ”. This is also further subdivided according to the framework structure, so that the mineral can be found in the sub-section "Chains of doubly connected rings of four", where it is only together with Phillipsite-Ca, Phillipsite-K and Phillipsite-Na the " Phillipsite group "with the system no. 9.GC.10 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the harmotome to the class of "silicates and Germanates" and there in the department of "structural silicates: zeolite group". Here it is in the group " Gismondin and allied species " with the system no. 77.01.03 to be found in the sub-section "Real Zeolites".

Crystal structure

Harmotome crystallizes in the monoclinic crystal system in the space group P 2 1 / m (space group no. 11) with the lattice parameters a  = 9.88  Å ; b  = 14.14 Å, c  = 8.69 Å and β = 124.8 ° and one formula unit per unit cell . Template: room group / 11

Education and Locations

Harmotome crystal group from the "Bellsgrove" pit near Strontian , Scotland (size 2.8 cm × 2.4 cm)

Harmotome forms hydrothermally in cavities of basalts , phonoliths , trachytes and gneisses . Other zeolites such as barite , calcite , galena , hyalophane , kaolinite , leucite , pyrite , quartz , sphalerite and strontianite occur as accompanying minerals .

As a relatively rare mineral formation, harmotome can sometimes be abundant at various sites, but overall it is not very common. Around 300 sites have been documented worldwide to date (as of 2019). In addition to its type locality Sankt Andreasberg and the nearby Bergmannstrost and Samson mines , the mineral also appeared in Lower Saxony in the Sankt Andreaskreuz mine at Beerberg . Other previously known sites in Germany include the nepheline-basalt quarry Höwenegg near Immendingen and the wllastonite-phonolite quarry Fohberg near Bötzingen in Baden-Württemberg, the Silberberg near Bodenmais and the area around Kemnath (Waldeck, Weha) in Bavaria, several quarries in Hausen ( casting ), Steffen Berg and upper ram home and on the mountain the book at Lindenfels in Hesse, the ancient lead mines Schwalenbach and welfare in the municipality Hellenthal North Rhine-Westphalia, several quarries in different places in Rhineland-Palatinate, the Great Horst and the district of St. Wendel in Saarland, the Schlickstal mine in the Drängetal near Hasserode in Saxony-Anhalt, several quarries near Bautzen and the Himmelsfürst treasure trove in Saxony, as well as quarries near Eisenach , Weitisberga and Schellbach in Thuringia.

Other locations include Tasmania in Australia, several locations in England , Scotland and Wales in Great Britain; in several regions of Italy ; on Honshū in Japan; British Columbia , Ontario and Quebec in Canada; on the northern and southern islands of New Zealand ; near Kongsberg (Buskerud), Nittedal (Akershus), near Oslo , in Trøndelag and on the Sjoa River in Norway; on the Mandlstein , the Hohe Tauern and Styria in Austria; in Russian Siberia ; Bohemia and Moravia in the Czech Republic; in the small area of ​​Bátonyterenye in Hungary; as well as in many regions of the United States .

See also

literature

Web links

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

Individual evidence

  1. ↑ a b Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: November 2019. (PDF 1720 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, November 2019, accessed December 30, 2019 .
  2. ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  705 (English).
  3. ^ David Barthelmy: Harmotome Mineral Data. In: webmineral.com. Accessed December 30, 2019 .
  4. ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  5. ↑ a b c d e f g h Harmotome . 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; 82  kB ; accessed on December 30, 2019]).
  6. ↑ a b c d e Harmotome. In: mindat.org. Hudson Institute of Mineralogy, accessed December 30, 2019 .
  7. ↑ Pierer's Universal Lexikon, Volume 8. Altenburg 1859, p. 44. at Zeno.org
  8. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed December 30, 2019 .
  9. ↑ a b List of locations for the Mineralienatlas and Mindat , accessed on December 30, 2019.