Bernalite

Bernalite
General and classification
other names	IMA 1991-032
chemical formula	Fe (OH) 3
Mineral class; (and possibly department)	Oxides and hydroxides
System no. to Strunz ; and to Dana	4.FC.05 ( 8th edition : IV / F.15) ; 03/06/05/03
Crystallographic Data
Crystal system	orthorhombic
Crystal class ; symbol	orthorhombic-dipyramidal; 2 / m 2 / m 2 / m
Space group	Immm (No. 71)
Lattice parameters	a = 7.544 Å ; b = 7.560 Å; c = 7.558 Å
Formula units	Z = 8
Physical Properties
Mohs hardness	4th
Density (g / cm 3 )	measured: 3.32; calculated: 3.35
Cleavage	Please complete
Break ; Tenacity	uneven to shell-like; brittle
colour	Yellow green, dark bottle green
Line color	Apple green
transparency	transparent to translucent
shine	Glass luster to diamond luster (when fresh); Greasy shine
Crystal optics
Refractive index	n = 1.92 to 1.94
Other properties
Chemical behavior	Soluble in acids

Bernalite is a very rare mineral from the mineral class of oxides and hydroxides . It crystallizes in the orthorhombic crystal system with the chemical composition Fe (OH) ₃ and is therefore chemically iron (III) hydroxide .

Etymology and history

Today's type material from Bernalit was already salvaged in 1920 by RT Slee from the "Propietary Mine" in Broken Hills , New South Wales , Australia . Slee sent the finds to the Australian mineralogist Frank Stillwell for identification. Stillwell recognized it as arsenopyrite surrounded by scorodite . The find was then kept for a long time in the Institute of Mineralogy at the University of Melbourne . In 1990 all finds were moved to the Museum of Victoria in Melbourne and re-examined in this context. Bernalite was discovered and described in 1993 by William D. Birch, Allan Pring, Armin Reller, Helmut W. Schmalle, who named the mineral after the British mineralogist John Desmond Bernal (1901–1971), to him for his services in the field of crystal chemistry to honor iron oxides and hydroxides .

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the bernalite belonged to the mineral class of "oxides and hydroxides" and there to the department of "hydroxides and oxidic hydrates (water-containing oxides with a layered structure)", where it together with dzhalindite and Söhngeit formed the unnamed group IV / F.15 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies the Bernalite in the category of "hydroxides (without U and V)". This is further subdivided according to the possible presence of hydroxide ions and crystal water as well as the crystal structure, so that the mineral according to its composition and structure is classified in the sub-section “Hydroxides with OH, without H ₂ O; corner-linked octahedron "can be found, where, together with Söhngeit and Dzhalindit, the now named" Söhngeit group "with the system no. 4.FC.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Bernalite to the class of "oxides and hydroxides" and there in the department of "hydroxides and hydroxides containing oxides". Here it can be found in the unnamed group 06.03.05 within the subsection “Hydroxides and hydroxides containing (OH) ₃ or (OH) ₆ groups”.

Crystal structure

Bernalite crystallizes orthorhombically in the space group Immm (space group no. 71) with the lattice parameters a = 7.544 Å , b = 7.560 Å and c = 7.558 Å as well as 8 formula units per unit cell . Template: room group / 71

properties

The mineral contains traces of silicon dioxide , lead (II) oxide , tin (II) oxide and carbon dioxide .

Bernalit is readily soluble in acids .

Education and Locations

It often occurs in conjunction with goethite ( iron oxide hydroxide ), and coronadite ( Lead - manganese - oxide on). Bernalite can be found in the Propietary Mine in Broken Hills, New South Wales, Australia. There are also three sites in Germany (two in Baden-Württemberg and one in Saxony ) and one site in Italy in the province of Genoa .

The reference mineral is kept in the Victoria Museum in Melbourne .

literature

William D. Birch, Allan Pring, Armin Reller, Helmut W. Schmalle: Bernalite, Fe (OH) ₃ , a new mineral from Broken Hill, New South Wales: description and structure In: American Mineralogist , 1993, No. 78, p . 827–834 ( PDF 1 MB )
Catherine A. McCammon, Eddy De Grave, Allan Pring: The magnetic structure of bernalite, Fe (OH) ₃ . In: Journal of Magnetism and Magnetic Materials. Volume 152, Chapters 1-2, January 1, 1996, pp. 33-39 doi : 10.1016 / 0304-8853 (95) 00456-4

Web links

Individual evidence

^ ^A ^b ^c William D. Birch, Allan Pring, Armin Reller , Helmut W. Schmalle: Bernalite, Fe (OH) ₃ , a new mineral from Broken Hill, New South Wales: description and structure In: American Mineralogist , 1993, no . 78, pp. 827-834 ( PDF 1 MB )
↑ ^a ^b ^c ^d ^e ^f ^g Bernalite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (eds.): Handbook of Mineralogy, Mineralogical Society of America, 2001 ( PDF 66.9 kB ).
↑ ^a ^b Webmineral - Bernalite (English)
↑ Mindat - Bernalite (English)

[Birch-et-al-1] A ^b ^c William D. Birch, Allan Pring, Armin Reller , Helmut W. Schmalle: Bernalite, Fe (OH) ₃ , a new mineral from Broken Hill, New South Wales: description and structure In: American Mineralogist , 1993, no . 78, pp. 827-834 ( PDF 1 MB )

[Datenblatt-2] ↑ ^a ^b ^c ^d ^e ^f ^g Bernalite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (eds.): Handbook of Mineralogy, Mineralogical Society of America, 2001 ( PDF 66.9 kB ).

[Webmineral-3] Webmineral - Bernalite (English)

[mindat-4] Mindat - Bernalite (English)