Leucophane

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Leucophane
Leucophanite, Aegirine-175723.jpg
Leucophanite, penetrated by a needle-like aegirine crystal , from the Poudrette quarry, Mont Saint-Hilaire , Québec, Canada (edge ​​length of the leucophan crystal approx. 4–5 mm)
General and classification
chemical formula NaCaBe [4] [F | Si 2 O 6 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9th DH.05 ( 8th edition : VIII / F.24)
04/05/02/04
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-disphenoidic; 222
Space group P 2 1 2 1 2 1 (No. 19)Template: room group / 19
Lattice parameters a  = 7.40  Å ; b  = 7.41 Å; c  = 9.99 Å
Formula units Z  = 4
Twinning Penetrating quadruplets, polysynthetic twins
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) measured: 2.96 to 3.07; calculated: 2.961
Cleavage completely after {001}, clearly after {100}, {010} and {201}
Break ; Tenacity shell-like to uneven; very brittle
colour whitish green, greenish white, deep green with a yellowish tinge, wine yellow
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.571
n β  = 1.595
n γ  = 1.598
Birefringence δ = 0.027
Optical character biaxial negative
Other properties
Special features Occasionally pink to blue-violet fluorescence , strong phosphorescence , pyroelectric

Leukophane is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the chemical composition NaCaBe [4] [F | Si 2 O 6 ].

Leukophan usually develops tabular to short prismatic crystals up to about three centimeters in length with a glass-like sheen on the surfaces. Furthermore, there are various twins such as interpenetrating quadruplets , polysynthetic and pseudo tetragonal twins. Leucophane also occurs in the form of radial, fibrous spherulites .

In its pure form, Leukophane is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also appear white and, due to foreign admixtures, take on a greenish-white, wine-yellow or deep green color with a yellowish tinge, with the transparency decreasing accordingly. His line color , however, is always white.

Etymology and history

The name Leukophan is a compound word from the ancient Greek terms λευκός leukós for "white" and φαίνω phaínō for "seem" or "appear". Leucophane is a mineral that appears predominantly white.

Leukophane was first discovered in 1829 on the island of Låven (Skådön; Lamö; Lamanskjaer) in the Langesundsfjord in the Norwegian province of Vestfold and described in 1840 by Jens Esmark .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the leukophane belonged to the mineral class of "silicates and germanates" and there to the department of "chain silicates and band silicates (inosilicates)", where it belonged together with Balangeroit , Gageit and Rait the unnamed group VIII / F.24 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 classifies leukophane in the category of "chain and band silicates (inosilicates)". However, this is further subdivided according to the structure of the chains, so that the mineral can be found according to its composition in the sub-section "Chain and band silicates with 4-periodic single chains, Si 4 O 12 ", where it is the only member of the unnamed group 9 .DH.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the leukophane to the class of "silicates and germanates", but there in the department of "group silicates: Si 2 O 7 groups, generally without additional anions". Here it is together with Fresnoite , Hardystonite , Jeffreyite , Meliphanite and Gugiaite in the " Fresnoite group " with the system no. 55.04.02 can be found in the subsection “Group silicates: Si 2 O 7 groups, generally without additional anions and with cations in [8] and lower coordination”.

Crystal structure

Leukophane crystallizes orthorhombically in the space group P 2 1 2 1 2 1 (space group no. 19) with the lattice parameters a  = 7.40  Å ; b  = 7.41 Å and c  = 9.99 Å and 4 formula units per unit cell . Template: room group / 19

properties

Under UV light , some leukophanes show a pink to blue-violet fluorescence . They can also be highly phosphorescent and pyroelectric .

Education and Locations

Leucophane (yellowish, center), natrolite (white), rhodochrosite (yellowish red) and aegirine (black) from Mont Saint-Hilaire, Québec, Canada

Leukophan forms in pegmatites and pyroxene - syenites , where he among other Aegirin , albite , analcime , Ankylit , Astrophyllit , Epididymit , fluorite , Katapleiit , natrolite , orthoclase , Polylithionit , rhodochrosite and Serandit socialized occurs.

As a rare mineral formation, leukophane could only be detected at a few sites, although around 60 sites are known to date (as of 2015). In addition to its type locality Låven, the mineral occurred in many other places in the province of Vestfold such as Farris and Lågendalen near Hedrum and Tjølling and Tvedalen in Langesundsfjord in Larvik municipality . In addition, leukophane occurs in Norway in some places in the Telemark province such as Risør on the island of Risøya.

Other locations include Ilimaussaq - Intrusion in the southwest of Greenland , on the island of Roume in Guinea , which belongs to the Îles de Los , in the Poudrette quarry on Mont Saint-Hilaire in Canada, on Mount Akzhaylyautas in the Tarbagatai Mountains in Kazakhstan, in the Chibinen and the Lovozero Massif in Russia, on the glacier Darai-Pioz (Darai-Pioz) in Alay Mountains in Tajikistan and Schytkawitschy in the municipality of Gomel Region in Belarus.

See also

literature

  • Axel Erdmann: Undersökning af leucophan, ett nytt mineral frän trakten af ​​Brewig i Norrige. In: Kongliga Svenska Vetenskaps-Akademiens Handlingar 1840, pp. 191–200 ( PDF 2.87 MB ; Swedish)
  • E. Cannillo, G. Giuseppetti, V. Tazzoli: The crystal structure of leucophanite. In: Acta Crystallographica Volume 23 (1967), pp. 255-259
  • E. Cannillo, G. Giuseppetti, V. Tazzoli: On the crystal structure of leucophanite. In: Acta Crystallographica Volume 25 (1969), pp. 993-994
  • Joel D. Grice, Frank C. Hawthorne: Refinement of the crystal structure of leucophanite. In: The Canadian Mineralogist Volume 27 (1989), pp. 193–197 ( PDF 404.5 kB )
  • Henrik Friis, Adrian A. Finch, Peter D. Townsend, David E. Hole, Hassane El Mkami: Ionoluminescence of leucophanite Volume 92, No. 2-3, pp. 254-260 doi : 10.2138 / am.2007.2167

Web links

Commons : Leukophane  - Collection of images, videos and audio files

Individual evidence

  1. ↑ 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.  641 .
  2. ↑ a b c d e f g h Leucophanite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 75 , 7 kB )
  3. ↑ a b c d Mindat - Leucophanite
  4. ↑ a b Database of luminescent minerals - Leucophanite
  5. ↑ Friedrich Tamnau : About the Leukophane. In: Annalen der Physik und Chemie Volume 48, 1839, p. 504 in the Google book search
  6. ↑ Karl Cäsar von Leonhard [Hrsg.]: Pocket book for the entire mineralogy, with regard to the latest discoveries Volume 61, 1841, p. 683 in the Google book search
  7. ↑ Mindat - Number of localities for Leucophanite
  8. ↑ Find location list for Leukophan in the Mineralienatlas and in Mindat