Heulandit

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Heulandit
Heulandite-19695.jpg
Heulandite druse from Jalgaon District , Maharashtra, India (size: 10.0 cm × 8.0 cm × 6.1 cm)
General and classification
chemical formula (X) 5 [Al 9 Si 27 O 72 ] · ≈24H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates - framework silicates (tectosilicates)
System no. to Strunz
and to Dana 		9.GE.05 ( 8th edition : VIII / J.23)
77.01.04.01 to 77.01.04.01d
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12) , Cm (No. 8) or C 2 (No. 5)Template: room group / 12Template: room group / 8Template: room group / 5
Lattice parameters see crystal structure
Formula units Z  = 1
Frequent crystal faces {010}, {100}, {001}, {20 1 }, {110}, {111}
Twinning according to {100} as a twin or contact level
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) measured: 2.10 to 2.20; calculated: 2.17
Cleavage completely after {010}
Break ; Tenacity slightly scalloped to uneven
colour colorless, white, gray, yellow, pink to red, orange, brown, black
Line color White
transparency transparent to translucent
shine Glass luster, pearlescent luster on cleavage surfaces
Crystal optics
Refractive indices n α  = 1.476 to 1.506
n β  = 1.479 to 1.510
n γ  = 1.479 to 1.517
Birefringence δ = 0.003 to 0.011
Optical character biaxial positive
Axis angle 2V = measured: 10 to 48 °

Heulandite is the collective name for an unspecified mineral of a mixed crystal series with the end members Heulandit-Ba , Heulandit-Ca , Heulandit-K , Heulandit-Na and Heulandit-Sr from the mineral class of "silicates" and recognized by the International Mineralogical Association (IMA) Germanate ". Structurally, the Heulandites belong to the framework silicates (tectosilicates) and there to the family of zeolites .

All members of the heulandite series crystallize in the monoclinic crystal system with the general chemical composition (X) 5 [Al 9 Si 27 O 72 ] · ≈24H 2 O, where X stands for the cations barium , calcium , potassium , sodium and strontium , which can represent each other in the formula ( substitution , diadochie), but are always in the same proportion to the other components of the mineral. For the individual end links, however, the chemical composition is also summarized as follows:

  • Heulandite Ba - (Ba, Ca, K) 5 (Si 27 Al 9 ) O 72 · 22H 2 O
  • Heulandite-Ca - (Ca, Na, K) 5 (Si 27 Al 9 ) O 72 · 26H 2 O
  • Heulandite-K - (K, Ca, Na) 5 (Si 27 Al 9 ) O 72 · 26H 2 O
  • Heulandit-Na - (Na, Ca, K) 6 (Si, Al) 36 O 72 · 22H 2 O
  • Heulandite-Sr - (Sr, Ca, Na) 5 (Si 27 Al 9 ) O 72 · 24H 2 O

Heulandite mostly develops leafy to tabular crystals , but also occurs in the form of granular to massive aggregates . Unharmed crystal surfaces have a glass-like sheen , whereas cleavage surfaces have a more mother-of-pearl shimmer . In its pure form, heulandite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also appear white and, due to foreign admixtures, take on a gray, yellow, pink to red, orange or brown to black color, the transparency decreasing accordingly. The line color , on the other hand, is always white.

With a Mohs hardness of 3.5 to 4, the Heulandite are among the medium-hard minerals that are just as easy to scratch with a pocket knife as the reference mineral fluorite (4) .

Etymology and history

Heulandite was first described by Henry James Brooke , who named the mineral after the English mineral collector and dealer John Henry Heuland (1778-1856).

In the course of the reorganization of the zeolite family in 1997, the end members of the heulandite mixed series were redefined and the predominant cations in the formula were appended as abbreviations.

The type locality for the individual minerals applies to

classification

In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Heulandite belonged to the division of "tectosilicates (tectosilicates) with zeolites", where they together with Barrerit , Brewsterit-Ba , Brewsterit-Sr , Epistilbit , Goosecreekit , clinoptilolite Ca, K and Na, Stellerit and stilbite Ca and Na, the group of "Blätterzeolithe I" with the system number. VIII / J.23 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also assigns the Heulandite to the category of “tectosilicates with zeolitic H 2 O; Family of zeolites ”. However, this is further subdivided according to the framework structure, so that the minerals can be found according to their composition in the sub-section "Tables with 4-4-1-1 structural units", where they are only found together with clinoptilolite-Ca, clinoptilolite-K and clinoptilolite - Well, the "Heulandit group" with the system no. Form 9.GE.05 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Heulandite to the class of "silicates and Germanates" and there in the department of "structural silicates: zeolite group". Here they are also in the group " Heulandite and allied species " with the system no. 77.01.04 to be found in the subsection "Real Zeolites".

Crystal structure

Crystal structure of heulandite, view along the b-axis
Crystal structure of heulandite, view along the a-axis
Crystal structure of heulandite, view along the c-axis

All Heulandites crystallize monoclinically in the space group C 2 / m (space group no.12 ) , Cm ( no.8 ) or C 2 (no.5) with the following lattice parameters with one formula unit per unit cell : Template: room group / 12Template: room group / 8Template: room group / 5

  • Heulandite-Ba - a  = 17.738 (3)  Å ; b  = 17.856 (2) Å; c  = 7.419 (1) Å and β = 116.55 (2) °.
  • Heulandite-Ca - a  = 17.72 Å; b  = 17.90 Å; c  = 7.43 Å and β = 116.4 °.
  • Heulandite-K - a  = 17.50 Å; b  = 17.82 Å; c  = 7.53 Å and β = 116.1 °.
  • Heulandite Na - a  = 17.76 Å; b  = 17.98 Å; c  = 7.40 Å and β = 116.4 °.
  • Heulandite-Sr - a  = 17.65 Å; b  = 17.88 Å; c  = 7.40 Å and β = 116.6 °.

Aluminosilicate framework

The Si 4+ and Al 3+ ions are tetrahedrally surrounded by four oxygen anions, so that the cations are in the center and the anions at the corners of the coordination polyhedron .

The (Al, Si) O 4 tetrahedra are linked at all four corners via shared oxygen ions to form a framework that has a negative (anionic) charge due to the incorporation of Al instead of Si. This is compensated for by the installation of cations in the cavities of the framework.

The Heulandit framework (framework type “HEU”) is made up of 10, 8, 5 and 4 rings and is characterized by a two-dimensional channel system. It is traversed in two spatial directions by channels that allow the passage of particles with a maximum diameter of 3.67 Å. The cavities in the framework can accommodate particles with a maximum diameter of 5.97 Å. The proportion of the accessible volume is 9.5% and the framework density is 17.5 tetrahedra / 1000 Å 3 .

Secondary building units

The HEU frame can be built from the secondary unit 4-4 = 1. The unit consists of 9 tetrahedra, a double ring of 4 (D4R) with an additional tetrahedron connected to both rings.

The HEU framework belongs to a family with the RRO framework (synthetic zeolite RUB-41). 4-4 = 1 units are connected to form chains in the direction of the z-axis. These chains are connected via rings of 4 and 5 in the x-direction to form a two-dimensional periodic unit (PerBU). These layers are connected to one another in the y-direction to form rings of 8 and 10. With Heulandit, these layers can be mapped onto one another with a 180 ° rotation, with the RRO framework with a simple translation in the y-direction.

Canals and caverns

An alternative description builds the scaffolding structure from larger building units, the composite building units . The HEU framework can be thought of as being made up of a structural unit (CBU) made up of 10 tetrahedra (double ring of 4 with 2 additional tetrahedra, which result in another four rings of 5).

Channels made of 10-rings run through the structure in the a-direction, 8-ring channels in a- and c-direction and result in a two-dimensional channel system in the ac-plane of the framework. 3.05 Å particles can diffuse through the framework in the a and c directions. The ten channels in the a direction allow the passage of particles with 3.67 Å.

At the intersection of the 8-ring canals there are caverns which are delimited by eight 4-rings, eight 5-rings and four 8-rings (area symbol [4 8 5 8 8 4 ]). The caverns are connected to one another in the a and c directions via the 8-ring. For this two-dimensional pore system the “pore descriptor” is {2 [4 8 5 8 8 4 ] [100] (8-ring), [001] (8-ring)}.

At the intersection of the 8-ring and 10-ring canals there are caverns that are delimited by eight 5-rings, two 8-rings and two 10-rings (area symbol [5 8 8 2 10 2 ]). The caverns are connected to one another via rings of 8 along the [102] axis and rings of 10 along the a-axis ([100]). For this two-dimensional pore system the “pore descriptor” is {2 [5 8 8 2 10 2 ] [102] (8-ring), [100] (10-ring)}. Particles up to 5.98 Å in diameter can be trapped in this cavern.

properties

When heated to over 210 ° C, heulandite loses part of its crystal water and behaves orthorhombically due to the resulting lattice contraction . In this form, the mineral is sometimes referred to as metaheulandite .

Education and Locations

Orange haylandite from Garrawilla Station, Coonabarabran , New South Wales, Australia (size: 4.5 cm × 2.9 cm × 1.3 cm)
Light yellowish brown Heulandite-Ca from Linópolis (municipality of Divino das Laranjeiras), Minas Gerais , Brazil (size: 4.8 cm × 3.0 cm × 2.2 cm)
Green- colored Heulandite Ca from Ahmednagar , Maharashtra, India (size: 7.2 cm × 4.5 cm × 4.2 cm) due to the storage of celadonite

Heulandite forms in cavities of basalt , heavily weathered andesites and diabase , but can also be formed during the devitrification of volcanic glasses and tuffs . Various apophyllites and zeolites as well as calcite and datolite occur as accompanying minerals .

As frequent mineral formations, Heulandites can generally be found at many sites, with a total of more than 1300 sites known so far (as of 2014). However, since these finds are rarely analyzed with sufficient precision, information on the individual English members with regard to the number of sites is accordingly inaccurate.

The Indian state of Maharashtra , where tabular crystals and steps up to 10 centimeters in size were discovered in the district of Nashik , but also in the districts of Jalgaon and Pune ( Poonah ) , are known for the extraordinary finds of heulandite .

In Germany, the mineral could be found in several places in the Bavarian Forest (Waldkirchen, Bischofsmais and Bodenmais), in the Hessian Odenwald (Mühltal), in the Lower Saxony Harz Mountains (Bad Harzburg, Sankt Andreasberg), near Königswinter in North Rhine-Westphalia and in a few places in Saarland, Rhineland-Palatinate, Saxony, Saxony-Anhalt, and Thuringia can be found.

In Austria, heulandite has so far been found mainly in various places on the Koralpe from Carinthia to Styria, the Hohe Tauern from Carinthia to Salzburg, in the Lower Austrian Waldviertel and in North Tyrol , in the Upper Austrian Mühlviertel and in the Vorarlberg mountain valley Montafon .

In Switzerland, Heulandit is mainly known from the cantons of Graubünden (Bregaglia, Vorderrheintal), Ticino (Valle Maggia), Uri (Reuss Valley, Urserental) and Valais (Binntal, Goms, Lötschental).

Other locations include the Antarctic, Argentina, Australia, Brazil, Bulgaria, Chile, China, Costa Rica, Denmark, Ecuador, Finland, France, Greece, Ireland, Iceland, Israel, Italy, Japan, Canada, Kazakhstan, Madagascar, Morocco, Mexico, Namibia, New Zealand, Nicaragua, Norway, Peru, the Philippines, Poland, Portugal, Réunion, Romania, Russia, Sweden, Slovakia, Slovenia, Spain, South Africa, Taiwan, Tanzania, Turkey, Czech Republic, Ukraine, Hungary, Uruguay, United Kingdom (UK), United States of America (USA) and Cyprus.

Heulandite could also be detected in rock samples from the Central Indian Ridge .

use

As true zeolites, Heulandites are also suitable as ion exchangers , molecular sieves and for many other technical applications due to their microporous lattice structure , but are now often produced synthetically, see also possible uses of zeolites .

See also

literature

  • HJ Brooke : On the comptonite of Vesuvius, the brewsterite of Scotland, the stilbite and the heulandite . In: Edinburgh Philosophy Journal . tape 6 , 1822, pp. 112–115 ( rruff.info [PDF; 249 kB ; accessed on April 15, 2018]).
  • Douglas S. Coombs, Alberto Alberti, Thomas Armbruster, Gilberto Artioli, Carmine Colella, Ermanno Galli, Joel D. Grice, Friedrich Liebau, Joseph A. Mandarino, Hideo Minato, Ernest Henry Nickel , Elio Passengeria, Donald R. Peacor, Simona Quartieri , Romano Rinaldi, Malcom Ross, Richard A. Sheppard, Ekkehart Tillmanns, Giovanna Vezzalini: Recommended nomenclature for zeolite minerals: report of the Subcommittee on Zeolites of the International Mineralogical Association, Commission on New Minerals and Mineral Names . In: The Canadian Mineralogist . tape 35 , 1997, pp. 1571–1606 ( rruff.info [PDF; 3.4 MB ; accessed on April 15, 2018] Heulandit series from p. 14).
  • John Leslie Jambor , Edward S. Grew, Andrew C. Roberts: New mineral names . In: American Mineralogist . tape 83 , 1998, pp. 1347–1352 ( rruff.info [PDF; 92 kB ; accessed on April 15, 2018] Heulandit series from p. 6).
  • Alf Olav Larsen, Fred Steinar Nordrum, Nicola Döbelin, Thomas Armbruster, Ole V. Petersen, Muriel Erambert: Heulandite-Ba, a new zeolite species from Norway . In: European Journal of Mineralogy . tape 17 , 2005, pp. 143–153 , doi : 10.1127 / 0935-1221 / 2005 / 0017-0143 ( unibe.ch [PDF; 873 kB ; accessed on April 15, 2018]).

Web links

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

Individual evidence

  1. ↑ a b c Alf Olav Larsen, Fred Steinar Nordrum, Nicola Döbelin, Thomas Armbruster, Ole V. Petersen, Muriel Erambert: Heulandite-Ba, a new zeolite species from Norway . In: European Journal of Mineralogy . tape 17 , 2005, pp. 143–153 , doi : 10.1127 / 0935-1221 / 2005 / 0017-0143 ( unibe.ch [PDF; 873 kB ]).
  2. ↑ a b c d e f 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.  707 .
  3. ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  914-915 .
  4. ↑ a b c d Heulandite . 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; 81  kB ; accessed on April 15, 2018]).
  5. ↑ a b c d e Mindat - Heulandite
  6. ^ IMA / CNMNC List of Mineral Names; March 2014 (PDF 1.5 MB)
  7. ^ A b Ch. Baerlocher, LB McCusker: Database of Zeolite Structures - Framework Type HEU
  8. ↑ a b Ch. Baerlocher, LB McCusker: Database of Zeolite Structures - Building scheme for HEU and RRO (PDF 576.6 kB) and Henk van Koningsveld: Schemes for Building Zeolite Framework Models (PDF 2.32 MB)
  9. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  792–793 (first edition: 1891).
  10. ↑ Mindat - Number of localities for Heulandite
  11. ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Dörfler Natur ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 276 .
  12. ↑ Find location list for heulandite at the Mineralienatlas and at Mindat
  13. ↑ Mindat - type locality Central Indian Ridge (MESO Mineral zone, Central Indian Ridge, Indian Ocean)