Molybdenite

Molybdenite, outdated also known as molybdenite, Eutomglanz water or lead, is a commonly occurring mineral from the mineral class of " sulfides and sulfosalts ." It crystallizes in the hexagonal crystal system with the composition of MoS2, is so chemically seen a molybdenum or molybdenum (IV ) sulfide.

Molybdenite usually develops hexagonal, tabular to scaly crystals, but also massive aggregates of lead- gray to blue- violet color.

The rare element rhenium is always in low concentrations (of ppm to 1 to 2 %) in place of molybdenum before. In addition, there are often admixtures of silver and gold. Molybdenite is dimorphic with Jordisite and polytype to molybdenite -2H and -3R molybdenite.

Special Features

Molybdenite is very similar in appearance and hardness of the graphite, but differs from this in the stroke color, which is black to steel gray, but greenish gray to bluish gray in the molybdenite in the graphite. Molybdenite also feels greasy and rubs off.

The mineral has a Mohs hardness of 1 to 1.5 and a density from 4.7 to 4.8 g/cm3. It is usually opaque to opaque. However, very tiny sheets are translucent and transparent under infrared light.

Molybdenum can be difficult to melt, before the blowtorch it is even infusible, but it colors the flame yellowish green ( Zeisiggrün ). In the mineral acids is only slightly soluble.

In contrast to graphite or graphene molybdenite is a semiconductor and purely paramagnetic.

Etymology and history

Molybdenite was not named after its chemical constituent molybdenum, but the Greek word μόλυβδος [ molybdos ] or μόλιβος [ mólibos ] "Lead ", which is preserved in a mo -ri -wo- do / moliu̯dos / already in Mycenaean Greek.

Classification

In the old classification of minerals (8th Edition) by Strunz molybdenite is still in the mineral class and department of " sulfides with the molar ratio of metal (M): sulfur ( S) ( selenium, tellurium ) <1: 1" sorted.

The mineral class remained in the new classification of minerals ( 9th edition ) the same. However, the minerals in this class have been partially redefined and divided the departments finer. Molybdenite has since been in the department " metal sulfides with M: S ≥ 1: 2" and the group "M: S = 1: 2; Cu, Ag, Au, Ni, Sn, platinum group elements (PGE ), Mo, W "

In the scheme of minerals by Dana molybdenite is in the department of " sulfide - selenide and telluride Including where Am Bn Xp, with (m n): p = 1:2 " ( translation: sulphides, selenides and tellurides with AmBn Xp and the molar ratio of ( n m ): p = 1:2, wherein A and B are cations and X = anion of the compound )

Education and Locations

Molybdenite is either formed in igneous rocks such as aplite, granite and pegmatite or by hydrothermal processes in vein deposits and porphyry. Accompanying minerals include anhydrite, chalcopyrite, fluorite, pyrite, quartz, and scheelite.

Locations include Afghanistan; several regions in Argentina; many regions in Australia; Brabant, Liège and Luxembourg in Belgium; Altenberg, Cínovec, Ehrenfriedersdorf and slag Walde ( Erzgebirge) in Germany; Finland; Travers Ella and Macchetto in Italy; several regions in Norway; at Nertschinsk ( Transbaikal region ) in Russia; Greenland; many regions in Austria; and many places North America.

Crystal structure

Molybdenite crystallizes in the hexagonal crystal system in space group P63/mmc with lattice parameters a = 3.161 Å and c = 12.295 Å and two formula units per unit cell.

The crystal structure of molybdenite similar to that of graphite, but which are present instead of the single graphene layers alternating layers of molybdenum and sulfur particles, which are easily displaceable against one another.

Use

Molybdenite is the principal ore for the recovery of molybdenum. Since it is the only mineral with a rewarding rhenium, it is also the most important rhenium.

In addition to graphite, it is the most important mineral for the manufacture of mineral lubricants ( solid lubricants ).

After so far mainly silicon and graphene were known as transistor material for microchips in future also molybdenite could take on this task according to previous research results of a Swiss research group led by Andras Kis of the EPFL. This should be similar to how to make graphs in a single atomic layer. At a film thickness of 0.65 nm it still is to have the same electron mobility as a silicon film of 2 nm. Energy efficiency should be higher by a factor of 100,000 against it. In contrast to the graph in which the time required for semiconductor band gap must be created artificially for the on and off switching of a transistor, it is the molybdenite already exists.