Arfvedsonite

from Wikipedia, the free encyclopedia
Arfvedsonite
Arfvedsonite, Orthoclase-183144.jpg
Group of twinned orthoclases (white) and multiple double-ended arfvedsonite crystals (black) from Mount Malosa, Zomba District , Malawi
(size: 80 mm × 52 mm × 35 mm)
General and classification
other names

Arfwedsonite

chemical formula NaNa 2 (Fe 2+ ) 4 Fe 3+ [(OH) 2 | Si 8 O 22 ]
Mineral class
(and possibly department)
Silicates and Germanates
System no. to Strunz
and to Dana
9.DE.25 ( 8th edition : VIII / F.08)
66.01.03c.09
Similar minerals Aegirin , Augit
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 10.01  Å ; b  = 18.08 Å; c  = 5.33 Å
β  = 104.1 °
Formula units Z  = 2
Twinning simple or lamellar twins parallel {100}
Physical Properties
Mohs hardness 5 to 6
Density (g / cm 3 ) measured: ≈ 3.3 to 3.5; calculated: [3.33]
Cleavage completely after {110}; Segregation after {010}
Break ; Tenacity uneven; brittle
colour dark blue to black, dark green on thin edges
Line color dark bluish gray to gray green
transparency translucent to opaque
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.652 to 1.699
n β  = 1.660 to 1.705
n γ  = 1.666 to 1.708
Birefringence δ = 0.014
Optical character biaxial negative
Axis angle 2V = 30 to 70 ° (measured); 70 to 80 ° (calculated)
Pleochroism very strong: blue-green, yellow-brown, gray-violet

Arfvedsonite (also Arfwedsonite ) is a rather seldom occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the monoclinic crystal system with the composition NaNa 2 (Fe 2+ ) 4 Fe 3+ [(OH) 2 | Si 8 O 22 ], and is thus chemically seen a sodium - iron silicate that is structurally to the double chain silicates and thus to Group of amphiboles with the general composition A 0-1 B 2 C 5 T 8 O 22 (OH) 2 , belongs. The unusual appearing of sodium twice at the beginning of the chemical formula of Arfvedsonite indicates this affiliation, since positions A and B in its crystal structure are each occupied by sodium.

Arfvedsonite is translucent to opaque and usually develops tabular to prismatic, striped crystals of up to 60 centimeters in length with a glass-like sheen on the surfaces. Occasionally it is also found in the form of radial, fibrous mineral aggregates . The mineral occurs exclusively in dark blue to black color, whereby thin edges can also shine through in dark green. Its line color also varies between dark bluish-gray and gray-green.

With a Mohs hardness of 5 to 6, arfvedsonite is one of the medium-hard minerals that, like the reference minerals apatite (5) and orthoclase (6), can be scratched with a good pocket knife or a steel file .

Arfvedsonite forms a mixed crystal row with Magnesio-Arfvedsonite (NaNa 2 (Mg, Fe) 4 Fe 3+ [(OH) 2 | Si 8 O 22 ]).

Etymology and history

Arfvedsonite was first discovered in the Ilimaussaq intrusion of the Kangerdluarssuq fjord in southwest Greenland and described in 1823 by Henry James Brooke (1771–1857), who named the mineral after the Swedish chemist Johan August Arfwedson .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the arfvedsonite belonged to the general department of " chain silicates and band silicates (inosilicates)", where together with Dellaventurait , Eckermannit , Ferrinybøit , Ferri-Ottoliniit , Ferriwhittackerit , Ferro-Eckermannit , Ferroglaukophan , Ferroleakeit , fluoro Ferroleakeit , fluoro-potassium Magnesio-Arfvedsonit , fluoro-magnesio-Arfvedsonit , fluoro Natriumpedrizit , Fluoronybøit , Glaukophan , Kaliumarfvedsonit , Kaliumleakeit , Kornit , Kôzulith , Leakeit , Magnesio-Arfvedsonit , Magnesioriebeckite , sodium Ferripedrizit , Sodium-Ferri-Ferropedrizit , Nybøit , Obertiit , Riebeckit , Ungarettiit the subgroup of "Alkali-Amphiboles" with the system no. VIII / F.08 within the amphibole group.

The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also classifies arfvedsonite in the category of “chain and band silicates (inosilicates)”. However, this is further subdivided according to the type of chain formation and / or belonging to larger mineral families, so that the mineral is classified in the sub-section “Chain and band silicates with 2-periodic double chains, Si 4 O 11 ; Amphibole family, clinoamphibole ”and there in the group of the“ alkali clinoamphibole, glaucophane eckermannite group ”with the system no. 9.DE.25 can be found.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns arfvedsonite to the class of "silicates and Germanates" and there in the department of "chain silicates: double unbranched chains, W = 2". Here it can be found in group 4, sodium amphiboles, within the subsection “Chain Silicates: Double unbranched chains, W = 2 amphibole configuration”.

Crystal structure

Arfvedsonite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 10.01  Å ; b  = 18.08 Å; c  = 5.33 Å and β = 104.1 ° as well as 2 formula units per unit cell . Template: room group / 12

properties

Due to its similarity in color and hardness, arfvedsonite can be confused with aegirine and augite . In contrast to arfvedsonite, however, aegirine has a light yellow-gray line and augite has a stronger birefringence with an optically positive character (arfvedsonite optically negative).

In front of the soldering tube , arfvedsonite melts very easily with a yellow flame color and formation of a magnetic pearl.

Modifications and varieties

Juddit from the Tirodi Pit, Madhya Pradesh , India ( overall size of the handpiece : 5.4 × 5.4 × 1.1 cm)

As Juddit a manganese is variety of Arfvedsonit referred. Juddit was named in 1908 by Lewis Leigh Fermor in honor of the British geoscientist John Wesley Judd .

Education and Locations

Arfvedsonite, eudialyte (orange) and microcline (white) from the Demix- Varennes mine , Montérégie (Québec), Canada
(field of view 2.2 × 2.9 mm)
Arfvedsonite and zircon from Mount Malosa, Zomba District, Malawi
( overall size of the step : 7.5 × 4.6 × 3.8 cm)

Along with aegirine and aegirine-augite, arfvedsonite is a typical mineral in light, alkaline igneous rocks such as granite and pegmatite . It is seldom formed through regional metamorphosis . In addition to aegirine, albite , katophorite , magnesiocatophorite , nepheline , riebeckite and quartz occur as accompanying minerals .

As a rather rare mineral formation, arfvedsonite can sometimes be abundant at various sites, but overall it is not very common. So far (as of 2013) around 270 sites are known to be known. In addition to its type locality Ilimaussaq / Kangerdluarssuq, where the mineral could be found in many places, Arfvedsonite occurred in Greenland at Ivittuut and Narsaarsuk in West Greenland and at Kangerlussuaq in East Greenland.

In Germany, arfvedsonite has so far been found at Katzenbuckel in the Odenwald (Baden-Württemberg), at the gabbro quarry (bear quarry) near Bad Harzburg (Lower Saxony) and in the "Brothers Unity" pit near Bösenbrunn in the Saxon Vogtland.

Other locations include Algeria, the Antarctic, Argentina, Armenia, Australia, Brazil, Chile, China, the Democratic Republic of the Congo, France and French Polynesia, Greece, Guinea, Guyana, India, Italy, Japan, Cameroon, Canada, on the Channel Island of Jersey, Kazakhstan, Kenya, Korea, Libya, Madagascar, Malawi, Morocco, Macedonia, Mongolia, Namibia, New Zealand, Niger, Nigeria, Norway, Portugal, on Réunion, in Romania, Russia, on St. Helena, in Saudi Arabia, Sweden, Spain, South Africa, Tajikistan, Czech Republic, Uganda, Ukraine, Hungary, Uruguay, the United Kingdom (Great Britain) and the United States of America (USA).

See also

literature

  • HJ Brooke: A description of the crystalline form of some new minerals. Arfwedsonite , in: The Annals of Philosophy , Volume 5 (1823), pp. 381–384 ( PDF 333.5 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. 797 .
  • Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 534 .

Web links

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

Individual evidence

  1. a b c d e f 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.  632 .
  2. Webmineral - Arfvedsonite
  3. a b c Arfvedsonite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 81.3 kB )
  4. a b c d Mindat - Arfvedsonite
  5. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 729 (first edition: 1891).
  6. ^ Mineralienatlas - localities for arfvedsonite
  7. Mindat - localities for arfvedsonite