Chapmanite

Chapmanit ( Höferit ) is a rare mineral from the mineral class of " silicates and Germanates ". It crystallizes in the monoclinic crystal system with the chemical composition SbFe3 2 [ OH | Si2O8 ] and developed predominantly earthy and massive mineral aggregates, rarely strip-shaped, tabular to prismatic crystals of yellow, yellow- green or green with yellow-green stroke color.

Etymology and history

Was first discovered Chapmanit in the " Keeley Frontier Mine" in South Lorrain ( Cobalt - Gowganda region) in the Timiskaming District ( Ontario, Canada) and described in 1924 by Thomas Leonard Walker ( 1867-1942 ), of the minerals by the Anglo- Canadian mineralogist Edward John Chapman (1821-1904) named.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Chapmanit belonged to the mineral class of " silicates and Germanates " and then to the Department of " island silicates with tetrahedral foreign anions ( Neso - Subsilikate ) " where he along with Bismutoferrit an independent group was formed.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Chapmanit also included in the category of " silicates and Germanates " and there in the department of " layer silicates ( phyllosilicates ) ". This division, however, is further subdivided by type of stratification, so that the mineral according to its construction in the subsection " layer silicates ( phyllosilicates ) with kaolinite layers composed of tetrahedral or octahedral nets " can be found where there is a namesake of the " Chapmanit Group" with the system number. Forms 9.ED.20 and the other members allophane, Bismutoferrit, chrysocolla, Imogolith and Neotokit.

The classification of minerals according to Dana assigns the Chapmanit in the class of " silicates and Germanates " and there in the department of " layer silicate minerals ." Here he is with Bismutoferrit in the " Bismutoferritgruppe " with the system no. ": With 1-1 layers of layers of six-membered rings phyllosilicates " to find 71.01.02d within the subdivision.

Education and Locations

Chapmanit formed secondarily in gneisses have been intruded by hydrothermal veins. Accompanying minerals include silver and stibnite.

Worldwide, Chapmanit so far (as of 2011) are detected in about 20 localities. Apart from its type locality " Keeley Frontier Mine" was found in the mineral Canada nor in the co- located in Timiskaming District " 404 Nipissing Mine". are, inter alia, Bräunsdorf and Freiberg in Saxony, Smilkov (Czech Republic) and the Keeley silver mine in Ontario ( Canada).

In Germany Chapmanit previously occurred only in the New Hope God's treasure trove at Bräunsdorf ( Oberschona ) in the Saxon Erzgebirge evident.

Other localities include Bohemia in the Czech Republic; Auvergne, Alsace and Lorraine in France; Tuscany in Italy; Kyūshū in Japan; the Alay Mountains in Kyrgyzstan; Bratislava, Slovakia; Asturias in Spain and Nevada in the United States.

Crystal structure

Chapmanit crystallizes in the monoclinic space group ( Raumgruppen-Nr. 12) with the lattice parameters a = 5.19 Å, b = 8.99 Å, c = 7.70 Å and β = 100 ° and two formula units per unit cell.