Hydroxyapophyllite (K)

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Hydroxyapophyllite (K)
Apophyllite- (KOH) -Pyrite-Tobermorite-44416.jpg
Pink-colored hydroxyapophyllite (K), accompanied by strongly striped pyrite and white, spherical tobermorite, from the Mina Noche Buena, Municipio Mazapil, Zacatecas , Mexico (size: 3.3 cm × 3.1 cm × 2.7 cm)
General and classification
other names
  • Hydroxyapophyllite
  • Apophyllite (KOH)
chemical formula
  • KCa 4 [(OH, F) | (Si 4 O 10 ) 2 ] • 8H 2 O
  • KCa 4 Si 8 O 20 (OH, F) • 8H 2 O
  • KCa 4 Si 8 O 20 (OH) • 8H 2 O
Mineral class
(and possibly department) 		Silicates and germanates ( phyllosilicates )
System no. to Strunz
and to Dana 		9.EA.15 ( 8th edition : VIII / H.01)
72.03.01.02
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol ditetragonal-dipyramidal; 4 / m  2 / m  2 / m
Space group P 4 / mnc (No. 128)Template: room group / 128
Lattice parameters a  = 8.978  Å ; c  = 15.83 Å
Formula units Z  = 2
Frequent crystal faces {110}, {101}, {001}
Twinning multiple twins possible
Physical Properties
Mohs hardness 4.5 to 5
Density (g / cm 3 ) 2.37 (measured); 2.36 (calculated)
Cleavage very perfect after {001}
Break ; Tenacity uneven; brittle [in each case by analogy to fluorapophyllite (K)]
colour colorless, white, pink, light yellow and light green tones
Line color White
transparency translucent to translucent, opaque
shine Glass gloss on {101}, pearlescent gloss on {001} and on cleavage surfaces
Crystal optics
Refractive indices n ω  = 1.542
n ε  = 1.543
Birefringence δ = 0.001
Optical character uniaxial positive
Other properties
Chemical behavior easily decomposed by acids such as HCl and HNO 3 to form a slimy residue [analogous to fluorapophyllite (K)]
Special features Exfoliates when heated [in analogy to fluorapophyllite- (K)]

Hydroxyapophyllite- (K) is a rarely occurring mineral from the group of apophyllites within the mineral class of " silicates and germanates ". It crystallizes in the tetragonal crystal system with the chemical formula KCa 4 [(OH, F) | (Si 4 O 10 ) 2 ] · 8H 2 O, and is thus chemically seen a hydrous potassium - calcium silicate with additional hydroxide or fluoride ion , the structurally belongs to the layered silicates (phyllosilicates). The constituents fluoride and hydroxide ions indicated in the round brackets can represent each other in the formula ( substitution , diadochy), but are always in the same proportion to the other constituents of the mineral.

Hydroxyapophyllite (K) is the end member of the hydroxyapophyllite (K) - fluorapophyllite (K) - mixed crystal series with variably exchangeable hydroxide ions (hydroxyapophyllite (K)) and fluoride ions (fluorapophyllite (K)). Hydroxyapophyllite (K) and fluorapophyllite (K) cannot be distinguished from one another either visually or by X-ray diffraction and in most cases also by optical methods. They can only be precisely assigned by chemical analysis.

Hydroxyapophyllite- (K) forms up to 15 cm large, isometric or {001} tabular crystals that are either colorless or show white, pink, yellowish or greenish hues. Like all minerals of the apophyllite group, hydroxyapophyllite (K) is found as secondary formations in amygdaloidal cavities or drusen in basalts , phonolites or other basic volcanic rocks , often accompanied by zeolites .

Etymology and history

Since countless occurrences in basaltic cavities are known, in which "apophyllites" are accompanied by fluorine-free paragenesis minerals such as prehnite and zeolites such as stilbit, heulandite and chabazite, the assumption arose that among these apophyllites there is also a fluorine-free, hydroxyl-dominant terminal member of the apophyllite group. An American working group led by the mineralogist Pete J. Dunn examined 50 apophyllite grades in the 1970s, and according to corresponding analyzes it turned out that in apophyllites of five locations the OH contents are greater than that of F, and the new mineral sought was therefore found has been. The mineral was recognized by the International Mineralogical Association (IMA) in 1978 and was described as hydroxyapophyllite by Pete J. Dunn, Roland C. Rouse , Julie A. Norrberg and Donald R. Peacor in the same year . It was named after the dominance of hydroxyl ions over fluoride ions and after the crystal-chemical relationship to other representatives of the apophyllite group. In 2008 Ernst Burke renamed the representatives of the apophyllite group, turning hydroxyapophyllite into "apophyllite (KOH)". This renaming was reversed in 2015 and the dominant monovalent cation was added to the mineral name as a suffix in brackets and the dominant non-tetrahedral anion was added to the mineral name as a prefix to delimit the individual species . The mineral name recognized by the IMA is now hydroxyapophyllite- (K).

Type material of the mineral is stored in the National Museum of Natural History , Washington, DC , USA (Catalog No. 137105, the holotype), the Natural History Museum , London in the United Kingdom (Catalog No. 1977,58); in the Geological Survey of Canada , Ottawa , (Catalog No. 14099); in the Royal Ontario Museum , Toronto , Canada , and at Harvard University , Cambridge , Massachusetts , USA.

classification

In the meanwhile outdated, but still in use 8th edition of the mineral systematics according to Strunz , hydroxyapophyllite (K) belongs to the mineral class of "silicates and germanates" and there to the department of "phyllosilicates", where together with fluorapophyllite (K) and fluorapophyllite (Na) the apophyllite group with system no. VIII / H.01 .

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 the hydroxyapophyllite (K) to the class of "silicates and germanates" and there in the department of "phyllosilicates" " a. This section is, however, further subdivided according to the structure of the layers, so that the mineral, according to its structure, can be found in the sub-section “Simple tetrahedral networks with 4, 5, (6) and 8 participating rings”, where it can be found together with fluorapophyllite (K ) and fluorapophyllite (Na) the apophyllite group with the system no. 9.EA.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns hydroxyapophyllite (K) to the class of "silicates and germanates" and there in the department of "layered silicate minerals". Here it is together with fluorapophyllite (K), fluorapophyllite (Na) and carletonite in the " apophyllite group (4- and 8-membered rings) " with the system no. 72.03.01 within the sub-section " Layered silicates: two-dimensional, unlimited layers with rings other than six-membered: 3-, 4-, or 5-membered rings and 8-membered rings ".

Chemism

For hydroxyapophyllite- (K) a simplified formula with KCa 4 Si 8 O 20 (OH) · 8H 2 O is given, the contents of 53.10% SiO 2 , 24.78% CaO, 5.20% K 2 O and 16.92% H 2 O required.

Hydroxyapophyllite- (K) is the hydroxyl-dominant analogue of the fluorine-dominant fluorapophyllite- (K), with which it forms a continuous series of mixed crystals .

Crystal structure

Structure of the minerals of the apophyllite group: __ Ca 2+ , __ ( Na , K ) + , __ O 2− , __ F - , __ H + , __ Si 4+

Hydroxyapophyllite- (K) crystallizes in the tetragonal crystal system in the space group P 4 / mnc (space group no. 128) with the lattice parameters a  = 8.978  Å and c  = 15.83 Å as well as two formula units per unit cell . Template: room group / 128

Hydroxyapophyllite- (K) has an unusual single-layer structure, which consists of endless layers or networks of SiO 4 tetrahedra parallel (001) (see also the adjacent figures). In contrast to the six-membered rings of the mica group, these layers are built up from four-membered and eight-membered rings of corner-sharing [SiO 4 ] 4− tetrahedra. The rings of four alternately point up and down with respect to the c-axis. The layers are linked to one another by large calcium ions that connect two oxygen atoms, one (OH, F) ion and two H 2 O molecules from each of the adjacent layers . The connection of the H 2 O molecules with the oxygen atoms of the SiO 4 tetrahedra takes place via hydrogen bonds. Each (OH, F) ion is surrounded by four coplanar calcium ions, while each potassium ion is surrounded by eight H 2 O molecules. In this way the tetrahedron layers change continuously with layers consisting of the large cations of calcium and potassium as well as F - / OH - and H 2 O molecules. The arrangement of the layers parallel (001) explains the very perfect cleavage of the hydroxyapophyllite (K) in this direction.

The crystal water is expelled in two steps between 300 ° C and 310 ° C and 400 ° C and 422 ° C.

properties

Costume and habitus of hydroxyapophyllite (K) crystals
Apophyllite isometric.png
isometric, pseudocubic crystal
Apophyllite tabular.png
tabular crystals (same colors represent the same surface shapes)

morphology

Hydroxyapophyllite- (K) almost always forms grown crystals up to 15 cm in size, which essentially appear in two different basic types with the main surface shapes {100}, {101} and {001} and {210} (see also the crystal drawings on the right ). When comparing with historical crystal drawings, it must be noted that the arrangement of the crystals in modern drawings is rotated by 45 ° compared to the previous morphological orientation. In addition to isometric cube-like crystals with the habit-defining, mostly in equilibrium surface forms {110} and {001} there are crystals that appear tabular due to the dominance of {001}. Due to the simultaneous occurrence of {110} and {210}, the surfaces of {110} often show clear and deep stripes parallel to the edges and rounding. In contrast to this is the opinion, which was already held at the end of the 19th century, that the striation of the Apophyllite is caused by structural defects with the formation of countless adjacent sub-individuals, with the individual blocks being offset by 1 ° to 3 °. The surfaces of {001} are often matt or even rough.

Overall, the morphology of hydroxyapophyllite- (K) is identical to that of fluorapophyllite- (K).

physical and chemical properties

In its pure form Hydroxyapophyllite- (K) is colorless and water-clear-transparent. Due to multiple refraction due to lattice construction defects or polycrystalline formation, the crystals are often white or show pink, yellow or greenish tones due to foreign atoms or inclusions of other minerals, with the transparency decreasing accordingly. Heavily altered hydroxyapophyllite (K) from Great Notch, New Jersey, USA, are even chalk white. The line color of the hydroxyapophyllite (K), however, is always white. The surfaces of the translucent to transparent crystals have a glass-like sheen on the surfaces of {110} , whereas on the surfaces of {001} and cleavage surfaces they have a pearlescent sheen . Hydroxyapophyllite- (K) shows a very perfect cleavage according to {001}, but breaks due to its brittleness like amblygonite , whereby the fracture surfaces are uneven. With a Mohs hardness of 4.5 to 5, hydroxyapophyllite (K) is one of the medium-hard minerals that, like the reference minerals fluorite and apatite, can be scratched more or less easily with a pocket knife. The measured density for hydroxyapophyllite (K) is 2.37 g / cm³, the calculated density is 2.36 g / cm³.

Like fluorapophyllite- (K), hydroxyapophyllite- (K) also shows a clear reaction before the soldering tube due to the splitting off of the crystal water . It flakes in a characteristic way and easily melts into white, blistered enamel, whereas on charcoal it becomes a clear, transparent ball. The flame only turns violet in the vicinity of the sample. Dulling in the flask with water being released. Easily decomposed by hydrochloric acid and nitric acid , difficult to decompose by sulfuric acid , forming a slimy to gelatinous residue that is more difficult to attack after glowing. The powder has a strong alkaline reaction, even after glowing.

Modifications and varieties

Hydroxyapophyllite (K) crystals from many localities are zoned continuously or discontinuously.

Education and Locations

Colorless hydroxyapophyllite (K) crystals on perimorphoses from prehnite to laumontite. Kandivali (Malad) Quarry, Malad, Mumbai, Maharashtra, India (size: 10.8 cm × 5.8 cm × 5.3 cm).

Hydroxyapophyllite- (K) occurs as a secondary formation in cavities and former gas bubbles in basalt or other volcanic rocks . Accompanying minerals are almost always zeolites such as stilbit , laumontite and scolezite, as well as prehnite , datolite and pectolite . Chalk-white, opaque hydroxyapophyllite- (K) from Great Notch and quarries at Bergen Hill and Prospect Park, all in New Jersey, appear to have been formed from fluorapophyllite- (K) by hydrothermal alteration.

Among the around 1100 sites known for "apophyllite" worldwide so far (as of 2016), there are only 85 localities in which the mineral hydroxyapophyllite (K) has been identified. At the time of the original publication, only five sites were known that provide hydroxyapophyllite- (K) in addition to the type locality.

The hydroxyapophyllite (K) type locality is the Ore Knob Mine at Ore Knob, Ashe County , North Carolina , USA . ( Coordinates of the Ore Knob Mine ). Here the hydroxyapophyllite (K) crystals form white crusts up to 1 cm thick, which lie on a chalcopyrite-pyrrhotite association. The steps reach sizes of up to 15 × 15 cm.

In Germany, hydroxyapophyllite (K) from nepheline basanites on the Wartberg near Längenau not far from Selb in the Fichtelgebirge , Bavaria , from void-rich basalts on the Rother Kopf near Roth not far from Gerolstein and from alkali basalts on the Höchstberg (Kelberg), both in the Eifel , Rhineland-Palatinate . In Austria , the mineral occurred at the Hocheck, Eibegggraben in the Fischbacher Alps near St. Jakob-Breitenau in Styria . Find places in Switzerland are unknown.

Apophyllite on prehnite, Fairfax Quarry, Centerville, Virginia / USA (size: 7.0 cm × 5.5 cm × 5.5 cm)

From the United States, in addition to the type locality, from the "Foote Lithium Co. Mine", Kings Mountain District, Cleveland County , North Carolina . Also from “Great Notch” near Little Falls Township , Passaic County , from “Prospect Park Quarry” near Prospect Park in Passaic County and the Franklin Mine near Franklin in the mining district of the same name, Sussex County , all New Jersey . Finally from the "Fairfax (Centerville) Quarry" at Centerville , Culpeper Basin, Fairfax County , Virginia .

From Mexico from the "Mina la Valenciana" near Guanajuato and from the "Mina la Luz" near La Luz, both in the Municipio Guanajuato , Guanajuato , and from the "Mina Noche Buena", Noche Buena , Municipio Mazapil , Zacatecas .

In India , the quarries and other outcrops in the triangle formed by the cities of Mumbai , Pune and Nashik in Maharashtra do not just produce world-class fluoroapophyllite (K) specimens. In particular, the Spilit quarry "Malad / Kurar" (also "Kandivali Quarry") near Malad not far from Mumbai, Mumbai Suburban district , as well as the "Pashan Quarries" in the Pashan Hills near Pashan in the Pune district have also provided wonderful specimens with hydroxyapophyllite (K) .

In South Africa , good hydroxyapophyllite (K) crystals have been recovered from the Kimberley Mine near Kimberley in Frances Baard (District) , Northern Cape Province , and from the Kalahari manganese ore fields in the Northern Cape Province . The sites in the Kalahari manganese ore fields include the "Wessels Mine" near Hotazel and the "N'Chwaning I Mine" and the "N'Chwaning II Mine" near Kuruman . The pale pink, cream colored and colorless crystals of these three sites reach 8 cm size and of Inesit , Ruizit , pectolite , Datolith , Orientit , quartz , aragonite , barite , celestite , calcite , Thaumasit , Sugilith and xonotlite accompanied.

The Mofjellet (Mofjell) mine near Mofjellet , Rana municipality , Nordland province in Norway , should be mentioned among the sites for hydroxyapophyllite (K) in Europe . In one of the ore lenses, within a 20 cm wide tectonic zone in cracks and druses, good steps with up to 2 cm large hydroxyapophyllite (K) crystals were found.

Hydroxyapophyllite (K) is also found in Australia , Chile , Finland , Israel , Italy , Japan , Canada , Kenya , Namibia , Romania , Russia , Spain , Czech Republic , Hungary , Ukraine and the United Kingdom as well as other locations in Mexico, Known to Norway, South Africa and the United States.

use

Due to their size, color, luster and paragenesis, steps with hydroxyapophyllite (K) crystals are primarily sought-after formations for collectors.

See also

literature

  • Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 739-740 (first edition: 1891).
  • Martin Okrusch , Siegfried Matthes : Mineralogy: An introduction to special mineralogy, petrology and deposit science . 8th edition. Springer, Berlin Heidelberg 2009, ISBN 978-3-540-78200-1 , p. 739-740 (first edition: 1983).
  • Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 803 (apophyllite).
  • Hydroxyapophyllite [Hydroxyapophyllite- (K)], In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF, 70 kB )

Web links

Commons : Hydroxyapophyllite- (K)  - Collection of pictures, videos and audio files

Individual evidence

  1. ^ A b c 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.  659 .
  2. ↑ a b c d e f g Hydroxyapophyllite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF, 70 kB )
  3. ↑ a b c d e f g h i j Pete J. Dunn, Roland C. Rouse, Julie A. Norrberg (1978): Hydroxyapophyllite, a new mineral, and a redefinition of the apophyllite group. I. Description, currences, and nomenclature. In: In: American Mineralogist , Volume 63, pp. 196-202.
  4. ↑ a b c d e f Pete J. Dunn, Wendell E. Wilson (1978): Nomenclature revisions in the Apophyllite group: Hydroxyapophyllite, Apophyllite, Fluorapophyllite. In: The Mineralogical Record , Volume 9, pp. 95-98 ( PDF, 2.85 MB ).
  5. ↑ Ernest AJ Burke (2008): Tidying up mineral names: an IMA-CNMNC scheme for suffixes, hyphens and diacritical marks. In: The Mineralogical Record , Volume 39, pp. 131-135.
  6. ↑ Frédéric Hatert, Stuart J. Mills, Marco Pasero, Peter A. Williams (2013): CNMNC guidelines for the use of suffixes and prefixes in mineral nomenclature, and for the preservation of historical names. In: European Journal of Mineralogy , Volume 25, pp. 113-115.
  7. ^ IMA / CNMNC List of Mineral Names; May 2016 (PDF 1.6 MB)
  8. ↑ Martin Okrusch , Siegfried Matthes : Mineralogie: An introduction to special mineralogy, petrology and deposit science . 8th edition. Springer, Berlin Heidelberg 2009, ISBN 978-3-540-78200-1 , p.  739-740 (first edition: 1983).
  9. ^ William Alexander Deer , Robert Andrew Howie , Jack Zussman : An introduction to the rock-forming minerals . 2nd Edition. Longman Scientific & Technical , Harlow (Essex) 1992, ISBN 0-582-30094-0 , pp.  382-383 .
  10. ^ A b Giselle F. Marriner, John Tarney, J. Ian Langford (1990): Apophyllite group: effects of chemical substitutions on dehydration behavior, recrystallization products and cell parameters. In: Mineralogical Magazine , Volume 54, pp. 567-577 ( PDF, 1.29 MB ).
  11. ↑ George Y. Chao (1971): The Refinement of the Crystal Structure of Apophyllite - Determination oh the hydrogen positions by x-ray diffraction. In: The American Mineralogist , Volume 56, pp. 1234-1242 ( PDF, 468 kB ).
  12. ^ Paul Ramdohr , Hugo Strunz : Klockmanns textbook of mineralogy . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp.  739-740 (first edition: 1891).
  13. ↑ Johann Rumpf (1879): About the crystal structure of apophyllite. In: Tschermaks Mineralogische und Petrographische Mitteilungen NF , Volume 2, pp. 369–391.
  14. ^ Berthold Ottens : India: Minerals - Locations - Deposits . 1st edition. Christian Weise Verlag, Munich 2011, ISBN 978-3-921656-76-1 , p.  277-283 .
  15. ↑ Carl Hintze : Handbook of Mineralogy. Second volume. Silicates and titanates . 1st edition. Verlag Veit & Co., Leipzig 1897, pp. 1731-1745.
  16. ^ Carl Rinman : Experiment with zeolite or guests (shower stone) . In: The Royal Swedish Academy of Sciences New Essays on Nature, Housekeeping, and Mechanics for 1784 . tape  5 . Verlag Johann Samuel Heinsius, Leipzig 1786, p. 51–68 ( available online in The Royal Swedish Academy of Sciences New Treatises from the Study of Nature, Household Art and Mechanics, pp. 51 ff. In Google Book Search).
  17. ↑ Mindat - Number of localities for the apophyllite group
  18. ↑ Mindat - number of localities for hydroxyapophyllite (K)
  19. ↑ a b List of locations for hydroxyapophyllite (K) in the Mineralienatlas and Mindat
  20. ↑ http://www.mindat.org/loc-17340.html Mindat - type locality for hydroxyapophyllite (K)
  21. ↑ Bruce Cairncross , Roger Dixon : Minerals of South Africa . 2nd Edition. Geological Society of South Africa , Linden (South Africa) 1999, ISBN 0-620-19324-7 , pp.  215 .
  22. ^ Alf Olav Larsen (1981): Hydroxyapophyllite from the Mofjellet mine, Mo i Rana, northern Norway (Contributions to the Mineralogy of Norway, No. 66). In: Norsk Geologisk Tidsskrift , Volume 61, pp. 297-300.