Laihunit

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Laihunit
General and classification
chemical formula Fe 2+ Fe 2 3+ (SiO 4 ) 2
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.AC.05 ( 8th edition : VIII / A.04)
03/01/05
Crystallographic Data
Crystal system monoclinic (pseudo-orthorhombic)
Crystal class ; symbol monoclinic prismatic: 2 / m
Space group P 2 1 / b
Lattice parameters a  = 4.805  Å ; b  = 10.189 Å; c  = 17.403 Å
α  = 91.0 °; β  = 90 °; γ  = 90 °
Formula units Z  = 12
Physical Properties
Mohs hardness 6th
Density (g / cm 3 ) 3.97 to 4.11
Cleavage good after {001}; completely according to {100} and {010}
colour dark brown, black
Line color pale brown
transparency opaque
shine Metallic luster
magnetism slightly magnetic and electromagnetic

Laihunite is a very rare mineral from the mineral class of " silicates and germanates ". It crystallizes in the monoclinic crystal system with the chemical composition Fe 2+ Fe 2 3+ (SiO 4 ) 2 and develops only small, opaque crystals in the millimeter range with a thick tabular to short prismatic habit and dark brown to black, metallic shining color.

Etymology and history

Was found for the first time Laihunit 1976 in iron - deposit at Laihe in Anshan (Liaoning) in China and described by the "Laihunite Research Group" from the Guiyang Institute of Geochemistry , also called the minerals by this locality.

classification

In the old (8th edition) and new systematics of minerals according to Strunz (9th edition) , the Laihunit belongs to the department of " island silicates (Nesosilicates)" and there to the Oliving group , formed from the minerals fayalite , forsterite , laihunite, Liebenbergite and Tephroit .

The revised 9th edition of Strunz's mineral systematics divides this department more precisely according to the presence or absence of further anions and the coordination of the cations involved . The Laihunit is accordingly in the sub-section of “Island silicates without further anions; with cations in octahedral [6] coordination ”and is still a member of the olive group there, which, however, has been expanded to include the minerals glaucochroit and cherry stone .

The systematics of minerals according to Dana , which is common in the English-speaking world , assigns the Laihunit to the division of " Island silicates: SiO 4 groups with all cations only in octahedral [6] coordination ", similar to the new Strunz'sche mineral systematics . The Oliving group, which can also be found there, consists of the members Fayalit, Forsterit, Laihunit, Liebenbergit and Tephroit, as in the old Strunzian system, but expanded to include olivine, for which the IMA / CNMNC is still lacking recognition.

Crystal structure

Laihunite crystallizes monoclinically in the space group P 2 1 / b with the lattice parameters a  = 4.805  Å ; b  = 10.189 Å; c  = 17.403 Å; α = 91.0 °; β and γ = 90 ° and 12 formula units per unit cell .

properties

Laihunite exhibits slight magnetic and electromagnetic properties.

Education and Locations

Laihunite is a secondary mineral and is formed by oxidation from fayalite in Precambrian , metamorphic iron deposits. There it occurs mostly in paragenesis with augite , quartz , hypersthenes , magnetite and plagioclase .

In addition to its type locality Laihe in China, Laihunit has so far been found at nine other sites (status: 2009): Near Charbonnières-les-Varennes in the French department of Puy-de-Dôme ; on the Ettringer Bellerberg near Ettringen (Eifel) in Germany; at Atami (Shizuoka) and Yugawara (Kanagawa) on the Japanese island of Honshū; as well as in Crystal Cove State Park , Cheyenne Mountain and North Sister Mountain in the USA.

See also

literature

Web links

Individual evidence

  1. ↑ a b c d e Handbook of Mineralogy - Laihunite (English, PDF 73.4 kB)
  2. ↑ a b American Mineralogist Crystal Structure Database - Laihunite (English, 1986)
  3. ↑ Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 3-921656-17-6 .
  4. ↑ American Mineralogist Crystal Structure Database - Laihunite (English, 1986)
  5. ↑ Mindat - Laihunite (English)