Hollandite
| Hollandite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Ba (Mn 4+ , Mn 2+ ) 8 O 16 |
|
Mineral class (and possibly department) |
Oxides and hydroxides |
|
System no. to Strunz and to Dana |
4.DK.05 ( 8th edition : IV / D.08) 07.09.01.01 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic 2 / m |
| Space group | I 2 / m (No. 12, position 3) |
| Lattice parameters |
a = 10.01 Å ; b = 2.87 Å; c = 9.75 Å β = 91.2 ° |
| Formula units | Z = 1 |
| Twinning | usually after {101} or {lO 1 } |
| Physical Properties | |
| Mohs hardness | 6th |
| Density (g / cm 3 ) | measured: 4.95; calculated: [4.93] |
| Cleavage | clear, prismatic |
| Break ; Tenacity | brittle |
| colour | black, gray-black to silver-gray |
| Line color | black |
| transparency | opaque |
| shine | Semi-metallic to metallic gloss, earthy matt |
Hollandite is a rather seldom occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the monoclinic crystal system with the idealized chemical composition Ba (Mn 4+ , Mn 2+ ) 8 O 16 , more precisely BaMn 2+ Mn 4+ 7 O 16 .
In nature, however, Hollandite always occurs with small proportions of other metal ions, which is why the formula is used in various sources with (Ba, K) (Mn, Ti, Fe) 8 O 16 or with (Ba, K, Ca, Sr) (Mn 4+ , Mn 3+ , Ti, Fe 3+ ) 8 O 16 indicated, whereby the elements potassium , calcium and strontium or titanium and iron indicated in the brackets can represent each other in the formula ( Diadochie ), but always in the same proportion to the other components of the mineral.
Hollandite is opaque in every form and develops mostly radial-ray, fibrous, grape-like to kidney or massive mineral aggregates , but also prismatic crystals with flat, pyramidal ends several centimeters long. Hollandite can also be found in the form of stalactitic aggregates and as star-shaped inclusions in quartz . The color of Hollandit fluctuates between black, gray-black to silver-gray, but the line color is always black. A semi-metallic to metallic luster can be seen on the surfaces of fresh samples . Older and weathered or bulky samples, on the other hand, are earthy matt.
With a Mohs hardness of 6, Hollandite is one of the medium-hard to hard minerals that, like the reference mineral apatite, can just be scratched with a knife.
Etymology and history
Hollandite was first discovered in the "Kajlidongri Mine" ( Jhabua district ) in the Indian state of Madhya Pradesh and described in 1906 by the British Lewis Leigh Fermor (1880–1954), who named the mineral after Thomas Henry Holland (1868–1947), the then Director of the "Geological Survey of India".
Type material of the mineral is kept among other things in the mineralogical collection of the Ruhr University Bochum .
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the hollandite belonged to the mineral class of "oxides and hydroxides" and there to the department of "oxides with the molar ratio of metal: oxygen = 1: 2", where it was used together with ankangite , Cesàrolith , Coronadit , Henrymeyerit , Kryptomelan , Mannardit , Manjiroit , Priderit , Redledgeit and Strontiomelan formed an independent group.
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 assigns the hollandite to the class of "oxides and hydroxides" and there into the department of "oxides with the molar ratio of metal: oxygen = 1: 2 and comparable “. However, this section is further subdivided according to the size of the cations involved and the crystal structure, so that the mineral is classified in the sub-section “With large (± medium-sized) cations; Tunnel structures "can be found where, together with Akaganeit , Ankangit, Coronadit, Henrymeyerit, Manjiroit, Mannardit, Priderit and Redledgeit, the" Hollandit group "named after him with the system no. 4.DK.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the hollandite to the class of "oxides and hydroxides", but there in the category of "multiple oxides". Here it is together with Kryptomelan, Manjiroit, Coronadit, Strontiomelan and Henrymeyerit in the "Kryptomelan group (hard, black, fine-grained)" with the system no. 07.09.01 to be found within the subsection of " Multiple Oxides ".
Education and Locations
Hollandit forms as a primary mineral in kontaktmetamorph modified manganese ore - deposits , but can also secondarily arise as weathering product previously incurred manganese minerals. Accompanying minerals include bixbyite , braunite , piemontite , scheelite and vanadinite .
As a rather rare mineral formation, hollandite can sometimes be abundant at various sites, but overall it is not very common. A total of around 200 sites are known to date (as of 2011). In addition to its type locality "Kajlidongri Mine" near Jhabua in Madhya Pradesh , the mineral occurred in India in several deposits in the vicinity of Vizianagaram in Andhra Pradesh ; at Balaghat , Bhandara and Chhindwara in the Madhya Pradesh type area; at Bahdra and Nagpur in Maharashtra and at Sundargarh in Orissa .
In Germany, hollandite was found mainly in the Black Forest , among others at Langenbrand, Wittichen , Eisenbach, Hammereisenbach and in the well-known Clara mine near Oberwolfach. Furthermore, the mineral could also be found near Wölsendorf (Upper Palatinate) in Bavaria, Ober-Rosbach in Hesse, Allendorf (Sundern) and Müsen in North Rhine-Westphalia, at Königsberg in Rhineland-Palatinate and near Ehrenfriedersdorf in the historic mining landscape of Graul and near Kamenz in Saxony be detected.
In Austria hollandite was previously found near Badersdorf in Burgenland; in the Friesacher Bürgergiltsteinbruch, on the Hüttenberger Erzberg and on the Sonntagsberg near Sankt Veit an der Glan in Carinthia and on the Huteralm in the Tyrolean Ködnitztal .
In Switzerland, the mineral has so far only occurred at Falotta in the Graubünden municipality of Tinizong-Rona and at Pipjitälli on the Pipji Glacier in Turtmann Valley (canton of Valais).
Other locations are in Angola, Australia, Belgium, Bolivia, Bosnia and Herzegovina, Brazil, Bulgaria, China, Costa Rica, Fiji, France, Greece, Ireland, Israel, Italy, Japan, Jordan, Canada, Kazakhstan, Madagascar, Morocco , Mexico, Namibia, Norway, Pakistan, Poland, Russia, Sweden, Slovakia, Spain, South Africa, Tanzania, Czech Republic, Hungary, the United Kingdom (Great Britain) and the United States of America (USA).
Crystal structure
Hollandite crystallizes monoclinically in the space group I 2 / m (space group no. 12, position 3) with the lattice parameters a = 10.01 Å ; b = 2.87 Å; c = 9.75 Å and β = 91.2 ° as well as one formula unit per unit cell .
See also
Individual evidence
- ↑ a b c Handbook of Mineralogy - Hollandite (English, PDF 66.6 kB)
- ↑ Webmineral - Hollandite (English)
- ↑ 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. 226 .
- ↑ Database-of-Raman-spectroscopy - Hollandite (sample from the Tangen Mine, Hurdalsjoen, Nannestad, Akershus, Norway by James Shigley)
- ↑ IMA / CNMNC List of Mineral Names - Hollandite (English, PDF 1.8MB; p. 122)
- ^ Ruhr-Universität Bochum - publications using materials from the Mineralogical Collection (W. Schreyer, A.-M. Fransolet, H.-J. Bernhardt (2001): Hollandite-strontiomelane solid solutions coexisting with kanonaite and braunite in late quartz veins of the Stavelot Massif, Ardennes, Belgium , in: Contributions to Mineralogy and Petrology , Volume 141, pp. 560-571)
- ↑ Mindat - Number of locations for Hollandit
- ↑ Mindat - Hollandite (English)
literature
- L. Leigh Fermor: Manganese in India , in: Transactions of the Mining and Geological Institute of India , Volume 1 (1906), pp. 69–131 (PDF)
Web links
- Mineral Atlas: Hollandit (Wiki)