Ilvaite (also Lelievre, Lievrit, Jenit or Yenit ) is a mineral from the mineral class of " silicates and Germanates ", which may be abundant in various localities in part, but overall is not widespread. It crystallizes in the monoclinic crystal system with the chemical composition Ca ( Fe2 ) 2Fe3 [O | OH | Si2O7 ] and most developed prismatic crystals, but also, radial and granular to massive mineral aggregates of black to black -gray color with black stroke color.
With a Mohs hardness of 5.5 to 6 ilvaite belongs to the medium-hard minerals that can be scratched with a steel file. The faces of the usually opaque crystals have a faint metallic luster. Fracture surfaces or aggregate forms, however, are dull. In thin layers ilvaite is translucent and shows a strong pleochroism, ie depending on the direction from which the light beam passes through the crystal, the mineral changes color from dark green to yellow - brown to dark brown.
Before the blowpipe ilvaite melts easily to a black, glassy and magnetic ball.
Etymology and history
Ilvaite at Torre di Rio, a cliff was first discovered south of the port of Rio Marina on the Italian island of Elba and described in 1811 named by Henrich Steffens, of the minerals by the old name of Elba ( Ilva, after living there earlier Ilvaten ) after he dismissed the elected by the French name Jenit or Yenit.
In the now outdated but still in use 8th edition of the mineral classification by Strunz the ilvaite belonged to the mineral class of " silicates and Germanates " and then to the Department of " group silicates ( Sorosilikate ) " where he and along with Hennomartinit, Itoigawait, lawsonite, Noelbensonit Woehlerite an independent group formed.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the ilvaite also included in the category of " silicates and Germanates " and there in the department of " group silicates ( Sorosilikate ) ". This division, however, is further subdivided by the type of group formation, the possible presence of other anions and the coordination of the cations, so that the mineral according to its composition and structure in the subsection " Si2O7 groups with additional anions; Cations can be found in octahedral coordination and greater " where it only forms the unnamed group 9.BE.07 together with Manganilvait.
The mainly common in English-speaking classification of minerals according to Dana assigns the ilvaite in the class of " silicates and Germanates " there, however, in the already fine divided department of " group silicates: Si2O7 Groups and O, OH, F, and H2O" a. Here he is as a name together with lawsonite in the " lawsonite - ilvaite group " with the system no. ": With cations and / or Si2O7 Groups and O, OH, F, and H2O > Coordination Group silicates " to find 56.02.03 and the other members Hennomartinit, Noelbensonit, Itoigawait and Manganilvait within the subdivision.
Education and Locations
Ilvaite forms in Kontaktmetasomatischen rocks and iron deposits in metamorphic limonites and dolomite. Accompanying minerals include quartz, magnetite, hedenbergite, sphalerite, fluorite.
Overall, ilvaite so far (as of 2011) are detected at around 170 localities. Apart from its type locality at Rio Marina mineral still occurred in Italy at several places in the provinces of Livorno and Grosseto in Tuscany, Sardinia and the Monzoni in Trentino and in the provinces of Salerno ( Campania ), Genoa (Liguria ), Sondrio and Varese ( Lombardy ), Turin, Verbano -Cusio -Ossola (Piedmont) on.
Noteworthy due to exceptional Ilvaitfunde is among other things the island of Serifos in Greece, where up to 30 cm long crystals were found. At its type locality Rio Marina after all, were up to 10 cm long crystals to light.
In Germany ilvaite found inter alia in Seelbach ( Herborn ) in Hesse, near Bad Harzburg and Clausthal- Zellerfeld in Lower Saxony, in Ahrbrück in Rhineland-Palatinate and in several places of the Saxon Erzgebirge.
In Austria, the mineral has been found only in Freiberg in Styria and at the Islitz Alp Umbaltal in Tirol and Switzerland so far only in Marmorera (Graubünden) and in the Binn Valley (Valais).
Other localities are Argentina, Australia, Bolivia, Bulgaria, Chile, China, Canada, France, Greenland, Iceland, India, Japan, Kosovo, Mexico, Mongolia, New Zealand, Norway, Romania, Russia, Slovakia, South Africa, Sweden, the Ukraine, England in the United Kingdom ( UK) and the United States of America (USA).
Ilvaite crystallizes in the monoclinic space group ( Raumgruppen-Nr. 14) with the lattice parameters a = 13.01 Å; b = 8.80 Å; c = 5.85 Å and 90.2 ° β = 4 and formula units per unit cell.