Quintinite
| Quintinite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Mg 4 Al 2 [(OH) 12 | CO 3 ] • 3H 2 O |
|
Mineral class (and possibly department) |
Carbonates and nitrates |
|
System no. to Strunz and to Dana |
5.DA.40 ( 8th edition : V / E.02) 16b.06.04 |
| Crystallographic Data | |
| Crystal system | hexagonal or trigonal |
| Crystal class ; symbol | hexagonal trapezoidal 622 or trigonal trapezoidal 32 |
| Space group | see crystal structure |
| Lattice parameters | see crystal structure |
| Formula units | see crystal structure |
| Physical Properties | |
| Mohs hardness | 2 |
| Density (g / cm 3 ) | measured: 2.141 |
| Cleavage | completely after {0001} |
| Break ; Tenacity | uneven; brittle |
| colour | colorless, yellow, orange-brown |
| Line color | White |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.533 (1) n ε = 1.533 (1) |
| Optical character | Quintinit-2H: uniaxially positive; Quintinit-3T: uniaxial alternating |
Quintinite is a very rarely occurring minerals from the mineral class of "carbonates and nitrates" with the chemical composition of Mg 4 Al 2 [(OH) 12 | CO 3 ] · 3H 2 O, that is a hydrated magnesium - aluminum - carbonate with additional hydroxide . From a crystallographic point of view, quintinite is a polytype , i.e. its crystal structure consists of a layer lattice with structural units crystallizing alternately in hexagonal or trigonal symmetry . In order to distinguish them, they are sometimes referred to as quintinite-2H or quintinite-3T , but are not considered to be independent modifications and minerals.
Quintinite develops thin to thick tabular or prismatic crystals , but also occurs in the form of pyramidal and rosette-shaped mineral aggregates . In its pure form, quintinite is colorless and transparent. However , it can also take on a yellow to orange-brown color due to foreign admixtures, whereby the transparency decreases accordingly.
Etymology and history
Quintinite was first discovered in the “Jacupiranga Mine” near Cajati in the Brazilian state of São Paulo ( Quintinit-2H ) and in the “Poudrette” quarry on Mont Saint-Hilaire in the Canadian province of Québec ( Quintinit-3T ). The mineral was first described in 1997 by George Y. Chao, Robert A. Gault, who named it after Quintin Wight (* 1935) to honor his contributions to the study of the geology of Mont Saint-Hilaire.
The polytypes Quintinit-2H and Quintinit-3T described by Chao and Gault were recognized as independent minerals by the International Mineralogical Association (IMA) in 1992 (register no.IMA 1992-028 and IMA 1992-029), but lost this status due to them the 1998 revision of the IMA guidelines on procedures for the recognition of minerals and mineral nomenclature. According to this, polymorphic forms of a mineral are only regarded as an independent species if their structures are also topologically different. However, if the structures differ only slightly from one atomic layer to the next due to lattice distortions or a change or disorder of the stacking sequence, these polymorphs are not considered to be independent.
The type material of the mineral is in the Canadian Museum of Nature in Ottawa (Catalog No. Quintinit-2H: CMNMI 81546, CMNMI 47266, CMNMI 81548; Quintinit-3T: CMNMI 81549) and in the Royal Ontario Museum in Toronto (Catalog No. Quintinit -2H: M46768, M46769, M46770; Quintinit-3T: M46771).
classification
In the outdated, but partly still in use, 8th edition of the mineral classification according to Strunz , quintinite belonged to the common mineral class of "carbonates, nitrates and borates" and there to the department of "water-containing carbonates with foreign anions ", where it was found together with barbertonite , caresite , charmarite , Manasseit , Sjögrenit and Zaccagnait the "Manasseit group" with the system no. V / E.02 formed.
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns the quintinite to the reduced class of “carbonates and nitrates”, but also to the department of “carbonates with additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the sub-section “With medium-sized cations”, where it is named after the “Quintinite group” with the system no. 5.DA.40 and the other members Caresit and Charmarit.
Also the systematics of minerals according to Dana , which is mainly used in the English-speaking area , assigns quintinite-2H and quintinite-3T, like the outdated Strunzian system, to the common class of "carbonates, nitrates and borates" and there in the department and subdivision of the same name of "carbonates" - hydroxyl or halogen ”. Here he is together with Caresit, Charmarit-2H and Charmarit-3T in the " Quintinit-Charmarit-Gruppe " with the system no. 16b.06.04 to be found.
Education and Locations
Quintinite formed by hydrothermal processes in miarolithischen cavities and pegmatite rock bodies having nepheline - syenites . Caresite and Charmarite appear as accompanying minerals .
In addition to his already described Type locality "Jacupiranga Mine" in Brazil and quarry "Poudrette" at Mont Saint-Hilaire in Canada quintinite has so far only on Cerro Sapo in the Bolivian province Ayopaya , in the Serpentine - magnesite - deposit "Dypingdal" at Snarum ( Commune Modum ) in the Norwegian province of Buskerud and in the iron mines "Korshunovskoye" near Schelesnogorsk-Ilimski (English Zheleznogorsk ) in the eastern Siberian administrative district of Irkutsk Oblast and " Kowdor Zheleznyi" on the Kola peninsula in Russia.
Crystal structure
Quintinit-2H crystallizes hexagonally in the space group P 6 3 22 (space group no. 182) with the lattice parameters a = 10.57 Å and c = 15.14 Å as well as 4 formula units per unit cell .
Quintinit-3T crystallizes trigonal in the space group P 3 1 12 (space group no. 151) or P 3 2 12 (space group no. 153) with the lattice parameters a = 10.56 Å and c = 22.71 Å and 6 formula units per unit cell.
See also
literature
- George Y. Chao, Robert A. Gault: Quintinite-2H, quintinite-3T, charmarite-2H, charmarite-3T and caresite-3T, a new group of carbonate minerals related to the hydrotalcite - manasseite group. In: The Canadian Mineralogist. Volume 35, 1997, pp. 1541–1549 ( PDF 1.02 MB )
- John Leslie Jambor , Edward S. Grew, Adrew C. Roberts: New mineral names. In: American Mineralogist. Volume 83, 1998, pp. 1347-1352 ( PDF 91.5 kB ; Quintinite p. 1)
- SV Krivovichev, VN Yakovenchuk, ES Zhitova, AA Zolotarev, YA Pakhomovsky, G. Yu. Ivanyuk: Crystal chemistry of natural layered double hydroxides. I. Quintinite-2H-3c from the Kovdor alkaline massif, Kola peninsula, Russia. In: Mineralogical Magazine. Volume 74, No. 5, October 2010, pp. 821-832 doi : 10.1180 / minmag.2010.074.5.821
Web links
- Mineral Atlas: Quintinit-2H and Quintinit-2H
- Database-of-Raman-spectroscopy - Quintinite
- American-Mineralogist-Crystal-Structure-Database - Quintinite (-2H)
- Webmineral - Quintinite-2H and Quintinite-3T
Individual evidence
- ↑ a b c d 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. 313 .
- ↑ George Y. Chao, Robert A. Gault: Quintinite-2H, quintinite-3T, charmarite-2H, charmarite-3T and caresite-3T, a new group of carbonate minerals related to the hydrotalcite - manasseite group. In: The Canadian Mineralogist. Volume 35, 1997, p. 1541 ( PDF 1.02 MB )
- ↑ Webmineral - Quintinite-2H and Quintinite-3T
- ↑ a b Mindat - Quintinite
- ^ IMA / CNMNC List of Mineral Names; October 2103 (PDF 1.5 MB; p. 142)
- ↑ Ernest H. Nickel, Joel D. Grice: The IMA commission on new minerals and mineral names: Procedures and guidelines on mineral nomenclature, 1998 , p. 5 In: The Canadian Mineralogist. Volume 36 ( PDF 328 kB )
- ↑ George Y. Chao, Robert A. Gault: Quintinite-2H, quintinite-3T, charmarite-2H, charmarite-3T and caresite-3T, a new group of carbonate minerals related to the hydrotalcite - manasseite group. In: The Canadian Mineralogist. Volume 35, 1997, p. 1542 ( PDF 1.02 MB )