Strict
| Strict | |
|---|---|
 |
|
| General and classification | |
| other names |
Barrandit |
| chemical formula | Fe 3+ [PO 4 ] • 2H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8th CD.10 ( 8th edition : VII / C.09) 04/40/01/02 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pcab (No. 61, position 2) |
| Lattice parameters | a = 10.12 Å ; b = 9.89 Å; c = 8.72 Å |
| Formula units | Z = 8 |
| Frequent crystal faces | {010}, {001}, {111}, {201}, {110} |
| Twinning | rarely after {201} |
| Physical Properties | |
| Mohs hardness | 3.5 |
| Density (g / cm 3 ) | measured: 2.84 to 2.87; calculated: 2.84 |
| Cleavage | good after {010}, indistinct after {001} |
| Break ; Tenacity | shell-like |
| colour | pink to purple, peach blossoms - to carmine red , greenish white, colorless |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.697 to 1.708 n β = 1.708 to 1.719 n γ = 1.741 to 1.745 |
| Birefringence | δ = 0.044 |
| Optical character | biaxial positive |
| Axis angle | 2V = 72 to 88 ° |
Strengite is a rather seldom occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the composition Fe 3+ [PO 4 ] · 2H 2 O, so it is chemically a water-containing iron (III) phosphate .
Strengite forms different crystal forms , although octahedral and strip-like forms that are stretched along the c-axis dominate. These can be several centimeters long and show a glass-like sheen on the surface . There are also fibrous, grape-like and spherical mineral aggregates .
In its pure form, Strengite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also appear white and, due to foreign admixtures, it can take on a pink to purple, peach blossom to carmine red or greenish white color, whereby the transparency decreases accordingly. However, its line color is always white.
Strengite forms a continuous mixed crystal series with variscite (Al [PO 4 ] · 2H 2 O) .
Etymology and history
Strengit was first discovered in the Eleanor mine near Gießen in Biebertal (Hessen) and described in 1877 by August Nies , who named the mineral after his teacher and professor of mineralogy Johann August Streng .
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Strengit belonged to the department of "water containing phosphates without foreign anions " where he along with Kolbeckit , Koninckite , Malhmoodit , Mansfieldit , metavariscite , Paraskorodit , Phosphosiderit , Skorodit , Variscit and Yanomamit the "Variscit Group" with the system no. VII / C.09 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), also assigns the Strengite to the category of “phosphates etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of phosphate, arsenate or vanadate complex (RO 4 ) to the water of crystallization contained , so that the mineral is classified according to its composition in the subsection “With only medium-sized cations; RO 4 : H 2 O = 1: 2 "can be found, where only together with Mansfieldite, Redondit , Skorodit, Variscite and Yanomamit the" Variscite group "with the system no. 8.CD.10 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the strictite to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here he is also together with Variscite, Skorodite, Mansfieldite and Yanomamite in the "Variscite group" with the system no. 40.04.01 to be found in the subsection of " Water-containing phosphates etc., with A 3+ XO 4 × x (H 2 O) ".
Crystal structure
Strengite crystallizes orthorhombically in the space group Pcab (space group no. 61, position 2) with the lattice parameters a = 10.12 Å ; b = 9.89 Å and c = 8.72 Å and 8 formula units per unit cell .
Modifications and varieties
The compound Fe 3+ [PO 4 ] · 2H 2 O is dimorphic and, in addition to the orthorhombic modification Strengite, also occurs as a monoclinic crystallizing phosphosiderite .
Education and Locations
Strengite forms in phosphate- containing , granitic pegmatites or secondarily through hydrothermal substitution from primary phosphate minerals. As Begleitminerale occur among other apatite , Beraunit , Bermanit , Dufrénit , Hureaulith , Kakoxen , Leukophosphit , Phosphosiderit , Rockbridgeite , Stewartit and Vivianit on.
As a rather rare mineral formation, Strengite can sometimes be abundant at various sites, but overall it is not very common. So far (as of 2013) around 240 sites are known. In addition to its type locality Grube Eleonore and the nearby Dünsberg in the vicinity of Gießen, the mineral occurred in Germany in the Clara mine in Baden-Württemberg; in several places around Hagendorf and other places in the Upper Palatinate Forest and Auerbach in the Upper Palatinate as well as at the Hühnerkobel in Bavaria; near Görzklinge / Kirschhausen , the Jakobssegen mine near Bremthal , the Rotlaufchen mine near Waldgirmes and near Essershausen in Hesse; at several sites in the Sauerland and Siegerland in North Rhine-Westphalia; near Rengersdorf and Hartmannsgrün / Oelsnitz / Vogtl. in Saxony as well as at Ullersreuth in Thuringia.
In Austria, Strengit has so far only been found in the whole valley in the Fischbacher Alps and near Herzogberg near Modriach in Styria.
The “Bull Moose Mine” near Custer in the US state of South Dakota, where violet crystals up to five millimeters in size emerged, is known for its extraordinary strengite finds.
Other locations include Argentina, Australia, Belgium, Bolivia, Brazil, Bulgaria, Chile, Finland, France and French Guiana, Iran, Italy, Japan, Cameroon, Canada, Liberia, Madagascar, Malaysia, Mali, Morocco, Mexico, Namibia, Portugal, Rwanda, Romania, Russia, Sweden, Senegal, Spain, South Africa, South Korea, Czech Republic, Uruguay, the United Kingdom (Great Britain) and the United States of America (USA).
See also
literature
- August Nies : Strengit, a new mineral , in: New Yearbook for Mineralogy, Geology and Palaontology , 1877, pp. 8–16 ( PDF 602.1 kB )
- Helmut Schrätze , Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 633 .
Web links
- Mineral Atlas: Strengit (Wiki)
- Database-of-Raman-spectroscopy - Stregite (database, contains, among other things, further literature)
- American-Mineralogist-Crystal-Structure-Database - Strengite (crystal structure database )
Individual evidence
- ↑ a b c d e Mindat - Strengite
- ↑ a b c d e 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. 478 .
- ↑ Webmineral - Strengite
- ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 633 .
- ↑ a b c d Strengite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 63.6 kB )
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 174–175 ( Dörfler Natur ).
- ↑ Mindat - Locations for Strengit