Hexaferrum

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Hexaferrum
General and classification
other names

IMA 1995-032

chemical formula (Fe, Os, Ru, Ir)
Mineral class
(and possibly department) 		elements
System no. to Strunz
and to Dana 		1.AF.05 ( 8th edition : I / A.13)
02/01/02/04
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Space group P 6 3 / mmc (No. 194)Template: room group / 194
Lattice parameters a  = 2.59  Å ; c  = 4.17 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 6 to 6.5 (VHN 50 = 652 (629–679) and 810 (741–880) for Ru- and Os-containing varieties)
Density (g / cm 3 ) calculated: 10.69 (Os rich 12.09; Ir rich 13.19)
Cleavage is missing
colour steel gray with a yellow tinge
Line color black
transparency opaque (opaque)
shine Metallic luster
magnetism magnetic

Hexaferrum is a very rarely occurring mineral from the mineral class of the "elements (including natural alloys or intermetallic compounds, carbides, nitrides, phosphides and silicides)" with the chemical composition (Fe, Os, Ru, Ir) and is therefore one from a chemical point of view natural alloy of iron , osmium , ruthenium and iridium , with the iron component predominating.

Hexaferrum crystallizes in the hexagonal crystal system , but has so far only been found in microcrystalline form as cubic or octahedral grains up to about 200 μm in size. The mineral is opaque in every form and of a steel-gray color with a tinge of yellow. The surfaces of the crystallites have a metallic sheen .

Etymology and history

Hexaferrum was first discovered in 1995 in the Chirynaisky massif, which is part of the Koryak Mountains on the Russian peninsula of Kamchatka . The first description was in 1998 by AG Mochalov, GG Dmitrenko, NS Rudashevsky, IV Zhernovsky and MM Boldyreva, who named the mineral after its hexagonal symmetry and its main component iron ( Latin: ferrum ).

Type material , i.e. mineral samples from the type locality , is kept in the Mining Museum of the State Mining University in Saint Petersburg (Russia).

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the hexaferrum belonged to the mineral class of "elements" and there to the department of "metals and intermetallic alloys (without semimetals)", where it was used together with osmium , rhenium , ruthenium and rutheniridosmin the "osmium series" with the system no. I / A.13 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 the hexaferrum in the "Metals and Intermetallic Compounds" section. However, this is further subdivided according to the predominant metals in the compound, which have been divided into metal families according to their related properties. Hexaferrum can be found here according to its composition in the subsection “Platinum Group Elements (PGE)”, where together with garutiite , osmium, rutheniridosmin and ruthenium, it forms the “ruthenium group” with the system no. 1.AF.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the hexaferrum to the class and to the division of the same name of "elements". Here it is together with osmium, ruthenium, rutheniridosmin, hexamolybdenum and garutiite in the " osmium group (space group P63 / mmc) " with the system no. 02/01/02 within the sub-section “Elements: Platinum Group Metals and Alloys”.

Chemism

On the basis of 11 grains with the help of the electron microscope (see also electron microscope ) the chemical composition was an average of 40.22% iron (Fe), 29.06% iridium (Ir), 16.40% osmium (Os), 9.60% ruthenium ( Ru), 3.55% rhodium (Rh), 0.98% platinum (Pt), 0.55% nickel (Ni), 0.39% copper (Cu), 0.06% cobalt (Co) and 0, 01% palladium (Pd) determined (all data in% by weight). This corresponds to the empirical formula (Fe 0.65 Ir 0.14 Os 0.08 Ru 0.08 Rh 0.03 Ni 0.01 Cu 0.01 ) Σ 1.00 or simplified (Fe, Os, Ru, Ir).

Crystal structure

Hexaferrum crystallizes hexagonally in the space group P 6 3 / mmc (space group no. 194) with the lattice parameters a  = 2.59  Å and c  = 4.17 Å as well as two formula units per unit cell . Template: room group / 194

The crystal structure corresponds to that of zinc , which also crystallizes in the hexagonal closest packing of spheres .

Education and Locations

At its type locality in mainly of dunite and harzburgite existing ultramafic rocks of the Massif, Chirynaisky Hexaferrum found in the form of cubic or octahedral grains as inclusions including in Cr spinel .

The only other known site to date is the Loma Peguera open-cast nickel ore mine ( 18 ° 59 ′ 24 ″  N , 70 ° 19 ′ 23 ″  W ) about 11 km northeast of Bonao in the Dominican Republic .

See also

literature

  • AG Mochalov, GG Dmitrenko, NS Rudashevsky, IV Zhernovsky, MM Boldyreva: Hexaferrum (Fe, Ru), (Fe, Os), (Fe, Ir) - a new mineral . In: Zapiski Vserossiskogo Mineralogicheskogo Obshchetstva . tape 127 , no. 5 , 1998, pp. 41-51 .
  • John Leslie Jambor , Vladimir A. Kovalenker, Andrew C. Roberts: New Mineral Names . In: American Mineralogist . tape 84 , no. 10 , October 1999, p. 1685–1688 ( minsocam.org [PDF; 62 kB ; accessed on January 11, 2018]).

Web links

Individual evidence

  1. ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  43 .
  2. ↑ a b c Stefan Weiss: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
  3. ↑ a b c d e f John Leslie Jambor , Vladimir A. Kovalenker, Andrew C. Roberts: New Mineral Names . In: American Mineralogist . tape  84 , no. 10 , October 1999, p. 1685–1688 ( minsocam.org [PDF; 62 kB ; accessed on January 11, 2018]).
  4. ↑ a b List of localities for Hexaferrum at the Mineralienatlas and at Mindat