Serandite
| Serandite | |
|---|---|
 |
|
| General and classification | |
| chemical formula |
|
|
Mineral class (and possibly department) |
Silicates and germanates - chain and band silicates |
|
System no. to Strunz and to Dana |
9.DG.05 ( 8th edition : VIII / F.18) 65.02.01.05 |
| Similar minerals | Pectolite NaCa 2 Si 3 O 8 (OH) |
| Crystallographic Data | |
| Crystal system | triclinic |
| Crystal class ; symbol | triclinic pinacoidal; 1 |
| Space group | P 1 (No. 2) |
| Lattice parameters |
a = 7.68 Å ; b = 6.89 Å; c = 6.75 Å, α = 90.5 °; β = 94.1 °; γ = 102.7 ° |
| Formula units | Z = 2 |
| Twinning | Contact twins after {110} |
| Physical Properties | |
| Mohs hardness | 5 to 5.5 |
| Density (g / cm 3 ) | measured: 3.34; calculated: 3.42 |
| Cleavage | completely according to {001} and {100} |
| Break ; Tenacity | uneven; brittle |
| colour | light pink to rose red, brown, black, colorless |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss to fat gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.668 n β = 1.671 n γ = 1.703 |
| Birefringence | δ = 0.035 |
| Optical character | biaxial positive |
| Axis angle | 2V = 39 ° (measured); 39 ° (calculated) |
Serandite (formerly Sérandite ) is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the triclinic crystal system with the idealized chemical composition NaMn 2+ 2 Si 3 O 8 (OH), so from a chemical point of view it is a sodium - manganese- silicate.
Structurally, Serandit belongs to the chain and band silicates with additional hydroxide ions . In addition, it forms a mixed crystal row with pectolite (NaCa 2 Si 3 O 8 (OH)) . Accordingly, the manganese contained in the formula is often caused by small amounts of in natural Serandit calcium replaced . Both can be expressed with the crystal chemical structural formula developed by Strunz in the form Na (Mn 2+ , Ca) 2 [Si 3 O 8 (OH)] or (Mn, Ca) 2 Na [Si 3 O 8 OH].
In its pure form, Serandite is colorless and transparent. However, due to multiple light refraction due to lattice construction defects or polycrystalline training, it can also be translucent white and, due to foreign admixtures, take on a light pink to pinkish-red, brown or black color. However, its line color is always white.
Serandite usually develops prismatic to needle-like as well as tabular or blocky crystals , but also occurs in the form of radial and massive mineral aggregates . Undamaged or unweathered crystal surfaces have a glass-like to grease-like gloss , cleavage surfaces, on the other hand, have a mother-of-pearl gloss and rough aggregates are matt.
With a Mohs hardness of 5 to 5.5, serandite is one of the medium-hard minerals that, like the reference minerals apatite (5) and orthoclase (6), can be scratched with a pocket knife or a steel file .
Etymology and history
Jules-Numa Mugnier Serand (1872–1933) is considered the discoverer of the mineral. As an assistant to Antoine Lacroix, he traveled to the island of Roume ( Guinea ), part of the Îles de Los , and found a pink ore there. Lacroix described the mineral in 1931 in his report on the geology of the island of Roume and named it after his assistant Serand, albeit in the spelling Sérandite (German corresponding to Sérandite ).
This spelling was adopted in various mineralogical scriptures and by 2015 also by the International Mineralogical Association . However, with the publication “Newsletter 28” of the IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) in December 2015, this spelling is discredited and replaced by the spelling Serandit (e).
The type material of the mineral is kept in the National Museum of Natural History in Washington, DC (Register No. 96515).
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Serandit belonged to the department of " chain and chain silicates (inosilicates)" where he collaborated with bustamite , Cascandit , Denisovite , Ferrobustamit , Foshagite , jennite , Pektolith , Tanohatait , Vistepit and wollastonite the "wollastonite group" with the system no. VIII / F.18 .
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 classifies serandite in the category of "chain and band silicates". However, this is further subdivided according to the type of chain formation, so that the mineral can be found according to its structure in the sub-section “Chain and band silicates with 3-periodic single and multiple chains”, where it is found together with bustamite, ferrobustamite, pectolite, tanohataite and wollastonite the "wollastonite group" with the system no. 9.DG.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the serandite to the "chain silicate minerals" department. Here it is also in the " wollastonite group " with the system no. 65.02.01 to be found in the subsection "Chain Silicates: Simple unbranched chains, W = 1 with chains P = 3".
Crystal structure
Serandite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a = 7.68 Å ; b = 6.89 Å; c = 6.75 Å; α = 90.5 °; β = 94.1 ° and γ = 102.7 ° as well as 2 formula units per unit cell .
Education and Locations
Serandit formed by hydrothermal processes in cavities of volcanic rocks such as nepheline - syenites , Pegmatiten or carbonatites . Besides nepheline, aegirine , analcime , arfvedsonite , astrophyllite , eudialyte , leukophanite , microcline , manganese-containing neptunite , sodalite and villiaumite were found as accompanying minerals .
As a rare mineral formation, Serandite has only been found at a few sites so far, with around 30 sites (as of 2013) being known and its type locality Roume is the only known site in Guinea to date .
The largest known and at the same time best crystals with a length of up to 20 centimeters were found on Mont Saint-Hilaire in Canada. Mont Saint-Hilaire is also known for its pseudomorphoses from rhodochrosite to serandite. Serandite crystals up to 6 centimeters long emerged in the “Yubileinaya” pegmatite dike on Mount Karnassurt Lowosero massif ( Lowosero tundra ) on the Russian Kola peninsula.
Other localities are among others in Australia, Brazil, Italy, Japan, Namibia, Norway, South Africa and the United States of America (USA).
See also
literature
- A. Lacroix (1931): Les pegmatites de la syénite sodalitique de l'île Rouma (archipelago de Los, Guinée française). Description d'un nouveau minéral (sérandite) qu'elles renferment , In: Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences , Volume 192, pp. 189–194 ( PDF 360.3 kB )
- WF Foshag (1931): New mineral names , In: American Mineralogist , Volume 16, pp. 343–344 ( PDF 126.3 kB )
Web links
Individual evidence
- ↑ a b IMA / CNMNC List of Minerals; May 2016 (PDF 1.6 MB)
- ↑ a b Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
- ↑ a b c d e 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. 636 .
- ↑ Webmineral - Sérandite
- ↑ a b Sérandite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 77.1 kB )
- ↑ a b c d Mindat - Sérandite
- ↑ Jules-Numa Mugnier Serand (1872-1933) In: Histoire et Patrimoine des Sources du Lac d'Annecy
- ↑ Joseph Serand I: Histoire et Patrimoine des Sources du Lac d'Annecy
- ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 732 (first edition: 1891).
- ^ IMA Commission on New Minerals, Nomenclature and Classification (CNMNC). NEWSLETTER 28 In: Mineralogical Magazine Volume 79 (7), December 2015, pp. 1859–1864 ( PDF 79.6 kB )
- ↑ Mindat - Number of localities for Sérandite
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 242 ( Dörfler Natur ).