Nepheline (also Eläolith or soapstone ) is a commonly occurring mineral from the mineral class of " silicates and Germanates ". It crystallizes in the hexagonal crystal system with the chemical composition (Na, K) [ AlSiO4 ] brown in different colors from white and gray to green, red and yellow. Nepheline may also occur colorless.
The mineral belongs to the group of Foide, which means that it is related to the alkali feldspars, but poor in silica (SiO2).
Nepheline is difficult to distinguish from quartz, decomposed, however contrary to this. In strong acids such as hydrochloric acid, with the resulting silica precipitates cloud-like
Etymology and history
Was first found nepheline 1801 at Monte Somma in Italy and described by René -Just Haiiy, of the mineral after the Greek word νεφέλη Nephele for " cloud" named because of its ability to form during the decomposition in strong acids precipitating silica clouds.
In the now outdated but still in use 8th edition of the mineral classification by Strunz the nepheline belonged to the mineral class of " silicates and Germanates " and then to the Department of " framework silicates ( tectosilicates ) " where he along with kaliophilite the " nepheline kaliophilite Group "with the system number. Formed VIII/J.02 and the other members kalsilite, Megakalsilit, Malinkoit, Panunzit, Trikalsilit and Yoshiokait.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the nepheline also in the class of " silicates and Germanates " and there in the department of " framework silicates ( tectosilicates ) without zeolitic H2O" one. This division, however, is further subdivided according to the possible presence of other anions, so that the mineral according to its composition in the subdivision of " framework silicates ( tectosilicates ) without additional anions " is to find where it as a name, the " Nephelingruppe " with the system no. Forms 9.FA.05 and the other members kaliophilite, kalsilite, Megakalsilit, Panunzit, Trikalsilit and Yoshiokait.
The mainly common in English-speaking classification of minerals according to Dana assigns the nepheline in the class of " silicates ", there, however, in the department of " framework silicates with Al- Si lattice ". Here it is also named the " Nephelingruppe " with the system no. 76.02.01 within the subdivision " framework silicates: Al- Si lattice, feldspar and related species " to find.
Education and Locations
Nepheline forms igneous rocks such as in alkaline syenite and pegmatite, rare in basalt and gneiss. It is together with leucite and similar an important, rock forming mineral.
Worldwide, nepheline so far (as of 2011) are detected in more than 600 localities. Apart from its type locality Monte Somma, the mineral in Italy still at Vesuvius and the Roccamonfina ( Caserta ) in Campania, in the Grotta del Cervo ( province of L' Aquila) in Abruzzo, in several places in Latium, at Lesina in Apulia, was on Monte Ferru in Sardinia, on Linosa ( Sicily) and in San Venanzo in Umbria found.
In Germany, nepheline found among others in the Black Forest and Odenwald Baden- Württemberg, in Franconia and the Upper Palatinate in Bavaria, near Fulda and Hofgeismar in Hesse, in Güntersen at Backsberg in Lower Saxony, in many places the Eifel region of Rhineland -Palatinate, at Lobau in Saxony, near Eckernförde and Kiel in Schleswig -Holstein and in Meiningen in Thuringia and the Thuringian Forest.
More Locations are Afghanistan, Angola, several find sites in East Antarctica, Argentina, Armenia, Azerbaijan, Australia, Bolivia, Brazil, Chile, China, Democratic Republic of Congo ( Zaire), Ecuador, Finland, France, Greenland, Guatemala, Guinea, India, Japan, Cameroon, Canada, Kazakhstan, Kenya, Kyrgyzstan, Colombia, Korea, Libya, Madagascar, Malawi, Mali, Morocco, Mexico, Mongolia, Myanmar (Burma ), Namibia, New Zealand, Norway, Paraguay, Peru, Poland, Portugal, Romania, Russia, Sweden, Slovakia, Somaliland, Spain, South Africa, Tajikistan, Tanzania, Czech Republic, Uganda, Ukraine, Hungary, Uzbekistan, the United Kingdom, the United States of America ( USA) and the Central African Republic.
Even in rock samples from the East Pacific Rise nepheline was found.
Nepheline crystallizes in the space group P63 hexagonal ( Raumgruppen-Nr. 173) with the lattice parameters a = 9.99 Å and c = 8.38 Å, and eight formula units per unit cell.
Nepheline has little significance as aluminum ore or additive in the ceramic industry.