Lizardite

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Lizardite
Lizardite-362595.jpg
Lizardite handpiece from Montville, Morris County, New Jersey, USA (size: ≈ 3.8 × 2.5 × 2.5 cm)
General and classification
chemical formula Mg 6 [(OH) 8 | Si 4 O 10 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.ED.15 ( 8th edition : VIII / H.27)
71.01.02b.02
Crystallographic Data
Crystal system monoclinic, trigonal or hexagonal, see crystal structure
Crystal class ; symbol Please complete!
Space group see crystal structure
Lattice parameters see crystal structure
Formula units see crystal structure
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) measured: 2.55 (3); calculated: 2.57
Cleavage completely after {001}
colour green, light yellow to white
Line color White
transparency translucent
shine Wax gloss
Crystal optics
Refractive indices n α  = 1.541 to 1.563
n β  = 1.565
n γ  = 1.553 to 1.568
Birefringence δ = 0.012
Optical character biaxial negative
Axis angle 2V = 37 to 61 ° (measured)

Lizardite is a rather rare mineral from the mineral class of " silicates and germanates ". Depending on the structural modification, it crystallizes in the monoclinic , trigonal or hexagonal crystal system with the chemical composition Mg 6 [(OH) 8 | Si 4 O 10 ] and, as a member of the serpentine group, belongs to the phyllosilicates .

Lizardite is mostly found in the form of fine-grained to massive mineral aggregates , but also develops tabular to pyramidal crystals with a waxy sheen on the surfaces. Its color varies from translucent green and light yellow to white.

Etymology and history

Lizardite was first discovered in the serpentinites on the eastern cliff on the Lizard Peninsula in the English county of Cornwall and described in 1956 by EJW Whittaker and J. Zussman, who named the mineral after its type locality .

classification

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Lizardite belonged to the department of "phyllosilicates (phyllosilicates)" where he collaborated with Amesit , antigorite , berthierine , Brindleyit , Carlosturanit , chrysotile , Cronstedtit , Dozyit , Fraipontite , Greenalith , Karpinskit , Karyopilit , Kellyit , Népouit and Pecorait the serpentine group with the system no. VIII / H.27 .

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 lizardite in the category of "phyllosilicates". This is, however, subdivided according to the structure of the layers, so that the mineral, according to its composition, can be found in the subsection "Layered silicates (phyllosilicates) with kaolinite layers, composed of tetrahedral or octahedral networks", where it is also a member of the serpentine group with system no . 9.ED.15 is.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , also classifies lizardite in the “layered silicate minerals” department. Here it is together with Karyopilith, Népouit and Greenalith in the " serpentine group (lizardite subgroup) " with the system no. 71.01.02b can be found in the subsection "Layered Silicates: Layers of six-membered rings with 1: 1 layers".

Education and Locations

Lizardite (green) with chrysotile vein (pearl white) from "Gordon's limestone quarry" near Montville , Morris County (New Jersey) , USA
(size approx. 8.89 × 5.08 × 5.08 cm)

Lizardite is typically produced by retrograde, i.e. retrograde metamorphosis ( Diaphthorese ), as a conversion product from olivine , Orthopyroxene or other ultramafic magmatic rocks. The accompanying minerals include chrysotile , brucite and magnetite .

As a rather rare mineral formation, lizardite can sometimes be abundant at various sites, but overall it is not very common. Around 260 sites are known to date. In addition to its type locality on the eastern cliff on the Lizard Peninsula , the mineral occurred in the United Kingdom in the "Coombe Farm" quarry near Henbury near Bristol in England and on Loch Scye in the north-western Highlands of Scotland.

In Germany, lizardite has so far been found at the "Michelsberg" quarry at Katzenbuckel in Baden-Württemberg, at the Zeilberg quarries near Maroldsweisach and "Heß" near Wurlitz in Bavaria, and at the Kalem volcano near Birresborn , Arensberg and Schellkopf near Brenk in Rhineland-Palatinate .

In Austria, the mineral was found in rock samples during the excavation of the Ehrental mountain tunnel near Klagenfurt in Carinthia, in the marble quarry near Kochholz ( Dunkelsteinerwald ) in Lower Austria and on the Brennkogel and Totenkopf in the Hohe Tauern mountains of Salzburg.

In Switzerland, lizardite has so far been discovered on the Wolfgang Pass , in the Oberhalbstein Valley and on the Julier Pass in the Canton of Graubünden and on the Geisspfad in the Binntal in the Canton of Valais.

Other sites are found in Egypt, Ethiopia, Argentina, Australia, Brazil, China, the Democratic Republic of the Congo, the Dominican Republic, Finland, France, Greece, Indonesia, Israel, Italy, Jamaica, Japan, Canada, Cuba, Morocco, New Zealand , Norway, Oman, Poland, Romania, Russia, Sweden, Slovakia, Spain, South Africa, Trinidad and Tobago Hungary and the United States of America (USA).

Lizardite could also be detected in rock samples from the Mid-Atlantic Ridge , more precisely at the northeastern edge of the “Markov Depth” within the “Sierra Leone Fracture Zone” ( Sierra Leone Threshold ).

Crystal structure

There are five structural modifications of Lizardite :

Crystallographic data for Lizardite
Surname Lizardite-1M Lizardite-1T Lizardite-6T 1 Lizardite-2H 1 Lizardite-2H 2
Crystal system monoclinic trigonal hexagonal
Crystal class m 3 m 3 6 mm 6th
Space group Cm P 31 m P 3 P 6 3 cm P 6 3
Lattice constants of the unit
cell 		a  = 5.31  Å
b  = 9.20 Å
c  = 7.31 Å
β = 90.0 ° 		a  = 5.33 Å; c  = 7.25 Å a  = 5.32 Å
c  = 43.61 Å 		a  = 5.32 Å
c  = 14.54 Å 		a  = 5.33 Å
c  = 14.37 Å
Number of formula units in the unit cell 1 0.5 3 1 1

See also

literature

  • EJW Whittaker, J. Zussman: The characterization of serpentine minerals by X-ray diffraction , in: Mineralogical Magazine , Volume 31 (June 1956), pp. 107–126 ( PDF 886 kB )
  • Ilija Krstanović: Crystal structure of single layer lizardite , in: Zeitschrift für Kristallographie , Volume 126 (1968), pp. 163–169 ( PDF 296.9 kB )

Web links

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

Individual evidence

  1. ^ A b c 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.  677 .
  2. ↑ a b Lizardite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 72 kB )
  3. ↑ a b c d Mindat - Lizardite
  4. ↑ Mindat - localities for Lizardite
  5. ↑ Mindat - Northeastern rim, Markov Deep, Sierra Leone fracture zone, Mid-Atlantic Ridge complex, Atlantic Ocean