Strunzite

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Strunzite
Strunzite-115068.jpg
Needle-shaped strunzite from Hagendorf, Upper Palatinate Forest, Bavaria, Germany
General and classification
chemical formula MnFe 2 3+ [OH | PO 4 ] 2 • 6H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.DC.25 ( 8th edition : VII / D.11)
11/22/09/01
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Room group (no.) P 1 (No. 2)
Lattice parameters a  = 10.23  Å ; b  = 9.84 Å; c  = 7.28 Å,
α  = 90.2 °; β  = 98.4 °; γ  = 117.4 °
Formula units Z  = 2
Twinning after {1 2 0}
Physical Properties
Mohs hardness 4th
Density (g / cm 3 ) measured: 2.52 (5); calculated: 2.49
Cleavage no
Break ; Tenacity uneven
colour white, light yellow, straw yellow, brownish yellow
Line color pale yellow to white
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.619 to 1.625
n β  = 1.640 to 1.670
n γ  = 1.696 to 1.720
Birefringence δ = 0.077 to 0.095
Optical character biaxial negative
Axis angle 2V = measured: 75 to 80 °; calculated: 86 °
Pleochroism weak: x = almost colorless, y = yellow-brown, z = dark yellow-brown

Strunzite is a rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the triclinic crystal system with the chemical composition MnFe 2 3+ [OH | PO 4 ] 2 · 6H 2 O, so it is a water-containing manganese - iron- phosphate with additional hydroxide ions .

Strunzite develops fibrous to needle-like crystals about two centimeters in length and a glass-like sheen on the surfaces, which are usually arranged in radial, tufted mineral aggregates . In its pure form, Strunzite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it appears predominantly white and due to foreign admixtures it can take on a light yellow, straw to golden yellow or brownish yellow color, the transparency decreasing accordingly.

Etymology and history

Strunzite was first found in 1957 in the "Cornelia pit" near Hagendorf near Waidhaus in Upper Palatinate (Bavaria) and described by Clifford Frondel , who named the mineral in honor of Karl Hugo Strunz (1910-2006) after him.

The type material of the mineral is stored at Harvard University in the USA (register no. 106288-106301).

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the strunzite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates with foreign anions ", where together with Beraunit it was the "strunzite -Beraunit Group "with the system no. VII / D.11 and the other members Bermanit , Burangait , Dufrénit , Ercitit , Ferristrunzit , Ferrostrunzit , Gormanit , Kakoxen , Kidwellit , Laubmannit , Matioliit , Meurigit-K , Meurigit-Na , Natrodufrénit , Oxiberaunit , Souzalite and Tinticit bildete .

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 Strunzite to the category of “phosphates etc. with 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 the additional anions to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4  = 1: 1 and <2: 1 ”can be found where the“ Strunzit Group ”with the system no. 8.DC.25 and the other members ferristrunzite , ferrostrunzite and metavauxite .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns strunzite to the class of "phosphates, arsenates and vanadates" and there to the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here he is also named in the " Strunzitgruppe " with the system no. 42.11.09 within the sub-section “Water-containing phosphates etc., with hydroxyl or halogen with (AB) 4 (XO 4 ) 3 Z q  × x (H 2 O)”.

Education and Locations

Strunzite needles on a matrix of iron hat and quartz

Strunzite forms as a typical secondary mineral in granitic pegmatite through weathering of various primary phosphates, but mostly triphylenes . Correspondingly, the mineral is also mostly found in paragenesis with triphyline, but also with laueit , rockbridge and many other Mn – Fe phosphates.

As a rare mineral formation, Strunzite could only be detected at a few sites, with around 100 sites being known so far (as of 2013). In addition to its type locality "Grube Cornelia" near Hagendorf, the mineral was also found in Germany on the Hühnerkobel , on the rose quartz rock near Pleystein and other places in Bavaria, as well as in rock samples during the expansion of the A46 near Hüsten and Uentrop (Arnsberg) in North Rhine-Westphalia.

Other locations are among others in La Victoria (San Alberto) in Argentina; near Mons in Hainaut, Belgium; in several regions of Minas Gerais in Brazil; at Orivesi in Finland; in the French provinces of Limousin and Midi-Pyrénées ; at Anloua in Cameroon; at Kobe in Japan; at Karibib in Namibia; Herzogberg near Kindberg in Austria; in the Portuguese regions of Guarda , Viana do Castelo and Viseu ; near Norrö in Södermanland in Sweden; at Brissago in Switzerland; in Czech Bohemia ; in England in the United Kingdom (Great Britain) and in the US regions of Alabama , Connecticut , Maine , New Hampshire , New Jersey , North Carolina and South Dakota .


Crystal structure

Strunzite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a  = 10.23  Å ; b  = 9.84 Å; c  = 7.28 Å; α = 90.2 °; β = 98.4 ° and γ = 117.4 ° as well as 2 formula units per unit cell .

See also

literature

Web links

Commons : Strunzite  - collection of images, videos and audio files

Individual evidence

  1. ↑ Webmineral - Strunzite (English)
  2. ↑ 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.  499 .
  3. ↑ a b Strunzite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 65.6 kB )
  4. ↑ a b c d Mindat - Strunzite (English)
  5. ↑ Mindat - Number of localities for Strunzite
  6. ↑ List of localities for Strunzite in the Mineralienatlas and Mindat