Stilbit
| Stilbit | |
|---|---|
.jpg) |
|
| General and classification | |
| other names |
Desmin |
| chemical formula |
|
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.GE.10 ( 8th edition : VIII / J.23) 77.01.04 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / m (No. 12) |
| Lattice parameters | see crystal structure |
| Formula units | Z = 1 |
| Twinning | Penetrating Twins |
| Physical Properties | |
| Mohs hardness | 3.5 to 4 |
| Density (g / cm 3 ) | 2.1 to 2.2 |
| Cleavage | completely after {010} |
| Break ; Tenacity | uneven |
| colour | colorless, yellowish, gray, brown |
| Line color | White |
| transparency | transparent to translucent edges |
| shine | Glass gloss |
Stilbit (also desmin or leaf zeolite ) is a collective name for the two minerals stilbit-Ca and stilbit-Na .
Both minerals belong to the mineral class of " silicates and germanates " and form the end links of a mixed series with the chemical compositions :
- Stilbit-Ca: NaCa 4 (Si 27 Al 9 ) O 72 · 28H 2 O
- Stilbit Na: Na 9 (Si 27 Al 9 ) O 72 · 28H 2 O
In simplified terms, the composition can also be given as a mixed formula in the form (Ca, Na) 9 [(Si, Al) 36 O 72 ] · 28H 2 O for stilbites with a predominant calcium content . If the sodium content is dominant , the order of the elements in the first bracket changes accordingly.
Both stilbites crystallize in the monoclinic crystal system and develop predominantly transparent to translucent, prismatic or tabular crystals as well as complex interpenetrating twins with a glass-like sheen on the surfaces. Often there are also sheaf-shaped or granular to massive mineral aggregates . In their pure form, Stilbit-Ca and Stilbit-Na are colorless and transparent. However, due to multiple light refraction due to lattice construction defects or polycrystalline training, they can also be translucent white and, due to foreign admixtures, take on a yellowish, pink to reddish and brown color.
Etymology and history
Stilbit was discovered by Axel Fredrik Cronstedt in 1756 and described by René-Just Haüy in 1796 and named after ancient Greek στίλβη stílbe , German 'shine, shimmer' because of its strong glass-like to mother-of-pearl-like sheen on the cleavage surfaces.
The name Desmin was coined in 1818 by August Breithaupt and refers to the characteristic bundle or sheaf-shaped aggregate form of the mineral ( ancient Greek δεσμή desme , German 'bundle' ).
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz belonged Stilbite Stilbite Ca and Na to the department of " framework silicates (tectosilicates), with zeolites" where they together with Barrerit , Brewsterit- (Ba) , Brewsterit- (Sr) , epistilite , goosecreekite , heulandite (Ba) , heulandite (Ca) , heulandite (K) , heulandite (Na) , heulandite (Sr) , clinoptilolite (Ca) , clinoptilolite (K) , Clinoptilolite (Na) and Stellerite the subgroup "Leaf Zeolite I" with the system no. VIII / J.23 within the zeolite group .
The valid since 2001 and by the International Mineralogical Association used (IMA) 9th edition of Strunz'schen systematic mineral also assigns Stilbite Stilbite Ca and Na in the department of the " framework silicates (tectosilicates) with zeolitic H 2 O; Family of zeolites ”. However, this section is further subdivided according to the type of binding form of the framework, so that the two minerals can be found according to their composition in the sub-section "Tables with 4-4-1-1 structural units", where they form the unnamed group 9 without further members .GE.10 form.
The systematics of minerals according to Dana , which is predominantly used in the English-speaking world , also classifies the Stilbite in the category of "framework silicates: zeolite group". Here they are together with Heulandit-Ca, Heulandit-Na, Heulandit-K, Heulandit-Sr, Heulandit-Ba, Clinoptilolite-K, Clinoptilolite-Na, Clinoptilolite-Ca, Stellerite and Barrerite in the group " Heulandite and related species " the system no. 77.01.04 to be found in the sub-section of "Real Zeolites".
Crystal structure
Both stilbites crystallize in the monoclinic crystal system in the space group C 2 / m (space group no. 12) with one formula unit per unit cell and the following, slightly different lattice parameters
- Stilbit-Ca: a = 13.64 Å ; b = 18.24 Å; c = 11.27 Å and β = 128.0 °
- Stilbit-Na: a = 13.61 Å; b = 18.33 Å; c = 11.25 Å and β = 127.7 °
The crystal structure of stilbite is similar to that of heulandite , which means that the formula units of stilbite are linked to form a framework. In the case of the stilbit, however, this consists of channels with tens rings parallel to the a-axis and eight rings parallel to the c-axis.
properties
morphology
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The crystals of the stilbit often have a characteristic, sheaf-shaped appearance with the apparently orthorhombic combinations {010}, {100} or {111}. In fact, however, these are monoclinic cross twins according to (010) and (001).
Chemical and physical properties
Stilbites are only sparingly soluble in hydrochloric acid.
Optical properties
Both end links show only minor differences in the optical properties:
| mineral | Refractive indices | Birefringence | opt. orientation | Dispersion of the opt. axes |
|---|---|---|---|---|
| Stilbit approx | n α = 1.484 to 1.500 n β = 1.492 to 1.507 n γ = 1.494 to 1.513 |
δ = 0.010 to 0.013 | biaxial negative | 76 ° to 78 ° |
| Stilbit-Na | n α = 1.479 to 1.492 n β = 1.485 to 1.500 n γ = 1.489 to 1.505 |
δ = 0.010 to 0.013 | biaxial negative | 76 ° to 78 ° |
Education and Locations
Stilbites are formed by hydrothermal processes in bladder spaces in volcanites (basalts and basalt almond stones), ore deposits or dikes or in the vicinity of thermal springs, but also in sedimentary rocks and are often found in paragenesis with cavansite , apophyllite and calcite and with various other zeolites .
Stilbit-Ca has so far been detected at 146 sites (as of 2009) and is therefore found much more frequently than Stilbit-Na, which has so far been detected at 14 sites.
Locations for Stilbit-Ca include Bertrix in Belgium; Santa Catarina in Brazil; Bavaria , Lower Saxony , Saxony and Thuringia in Germany; France ; England , Northern Ireland and Scotland in Great Britain; Nova Scotia and Québec in Canada; India ; several regions in Italy ; Styria and Tyrol in Austria; the regions of the Urals and Eastern Siberia in Russia; Sweden ; Switzerland ; Bohemia and Moravia in the Czech Republic; Ukraine ; Hungary ; as well as many regions in the US .
Locations for Stilbit-Na include South Australia and Victoria in Australia; India; Piedmont and Sardinia in Italy; as well as some regions of the USA.
See also
literature
- R.-J. Haüy: Traité de Minéralogie . tape 3 . at Louis Bookstore, Paris 1801, p. 161–166 (French, rruff.info [PDF; 378 kB ; accessed on July 9, 2019]).
- Stilbite- (Ca) . 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; 81 kB ; accessed on July 9, 2019]).
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 793 (first edition: 1891).
- Petr Korbel, Milan Novák: Mineral Encyclopedia (= Villager Nature ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 277 (stilbit-ca).
Web links
- Mineral Atlas : Stilbit-Ca and Stilbit-Na (Wiki)
- David Barthelmy: Stilbite-Ca Mineral Data. In: webmineral.com. Retrieved July 9, 2019 .
- David Barthelmy: Stilbite-Na Mineral Data. In: webmineral.com. Retrieved July 9, 2019 .
- Stilbite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on July 9, 2019 .
Individual evidence
- ↑ a b c d Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: May 2019. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2019, accessed May 20, 2019 .
- ↑ 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 (English).
- ↑ a b Martin Okrusch, Siegfried Matthes: Mineralogie. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 128 .
- ↑ Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 200 (keyword Desmin).
- ↑ a b Stilbite-Ca. In: mindat.org. Hudson Institute of Mineralogy, accessed July 9, 2019 .
- ↑ a b Stilbite-Na. In: mindat.org. Hudson Institute of Mineralogy, accessed July 9, 2019 .