Romanèchit

Romanèchit
	Romanèchite, found in: Marquette County , Michigan / USA .
General and classification
chemical formula	(Ba, H 2 O) 2 (Mn +4 , Mn +3 ) 5 O 10
Mineral class; (and possibly department)	Oxides
System no. to Strunz ; and to Dana	04.DK.10 ( 8th edition : IV / D.09) ; 07.09.02.01
Crystallographic Data
Crystal system	monoclinic, prismatic
Crystal class ; symbol	monoclinic prismatic; 2 / m
Space group	C 2 / m (No. 12)
Lattice parameters	a = 13.929 Å ; b = 2.8459 Å; c = 9.678 Å ; β = 92.39 °
Formula units	Z = 3
Physical Properties
Mohs hardness	5 to 6 (VHN 100 = 514 to 715)
Density (g / cm 3 )	measured: 4.70 to 4.74; calculated: [4.90]
Cleavage	is missing
Break ; Tenacity	uneven
colour	gray, anthracite to black
Line color	Brown black
transparency	opaque
shine	semi-metallic to matt
Other properties
Chemical behavior	soluble in HCl with evolution of chlorine

Romanechite is a common mineral from the mineral class of oxides and hydroxides . It crystallizes in the monoclinic crystal system with the chemical composition (Ba, H ₂ O) ₂ (Mn ⁺⁴ , Mn ⁺³ ) ₅ O ₁₀ .

Romanèchite is opaque in every form and rarely develops small, pronounced crystals in the form of needles. Mostly it forms grape-shaped aggregates of gray to anthracite-like or black color.

The mineral is an important manganese ore and forms the main component of psilomelan , which is no longer viewed as a separate mineral, but as a mixture of various manganese oxides, such as romanechite, hollandite and others. For this reason, Romanèchit cannot be regarded as a variety of psilomelan, or the two names should not be used synonymously.

Its Mohs hardness is 5 to 6 and its density is in the range of 4.7 to 4.9 g / cm ³ .

Etymology and history

Romanechite (Museo de La Plata)

Romanèchite was first discovered in the manganese deposit near the municipality of Romanèche-Thorins in the French department of Saône-et-Loire and described in 1900 by Antoine Lacroix , who named the mineral after its type of locality .

classification

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 Romanechite in the extended class of oxides, with a metal-to-oxygen ratio of 1: 2, medium-sized to large cations, which also have a tunnel structure. Here it forms the group 04.DK.10 with Kryptomelan , Strontiomelan and Todorokit .

Romanechite is classified in a very similar way in the Dana system of minerals , which is mainly used in the English-speaking world . Here the mineral falls into the class of multiple oxides, where it can be found in the cryptomelane group under the number 07.09.02.01.

Crystal structure

Romanèchite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a = 13.93 Å ; b = 2.85 Å; c = 9.68 Å and β = 92.4 ° as well as two formula units per unit cell . Template: room group / 12

The manganese oxide forms an octahedral framework in the romanechite, whereby the negative charge excess caused by the Mn (II) is not compensated by Mn (IV), but by the storage of cations in the large tunnel structure. The structure is similar to that of zeolites . Despite the similarity of the chemical composition and the crystal structure, no mixed crystals are known between romanèchite, hollandite , coronadite , todorokite and woodruffite .

properties

The water stored in the Romanèchit tunnel structure escapes at over 200 ° C. The mineral dissolves in concentrated hydrochloric acid, with the development of chlorine (cf. the chemical reactions of manganese (IV) oxide ).

Education and Locations

Romanechite is a weathering product of magnesium-containing oxides, carbonates or silicates. It is typically associated with hematite , barite , pyrolusite , quartz and other manganese oxides.

Romanechite is a widespread mineral and occurs in many manganese deposits around the world. Larger, historical stages are mainly known from Romanèche , Saône-et-Loire / France . Other sites are Elgersburg and Öhrenstock in Thuringia, as well as the manganese ore deposits of Cia turi / Georgia and Nikopol / Ukraine , as well as Lead Geo and the Horney Islands in Scotland .

use

Romanechite is an important manganese ore. It is mainly used for the production of steel .

literature

Antoine Lacroix : VII. Sélénites, téllurites, manganites et plumbates b) Manganites: romanéchite . In: Collection de Minéralogie du Muséum d'Histoire Naturelle Laboratoire de Minéralogie . 2nd Edition. Paris 1900, p. 28–29 ( rruff.info [PDF; 269 kB ]).
F. Zambonini , V. Cagliotti: Nuove ricerche sulla composizione chimica della romanechite . In: Periodico di Mineralogia . 1931, p. 73-80 .
Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 323 .

Web links

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

Individual evidence

^ ^A ^b 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. 227 .
↑ ^a ^b Romanèchite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 72 kB ; accessed on May 10, 2018]).

[StrunzNickel-1] A ^b 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. 227 .

[Datenblatt-2] Romanèchite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 72 kB ; accessed on May 10, 2018]).