Limonite

Limonite, also known as limonite or brown iron ore, is a very common -to-find, iron and hydrous iron oxides such as goethite mixture of different, lepidocrocite and various other hydrated iron oxides. In addition, in some localities also admixtures of hematite were found. Therefore, limonite is no longer considered a separate mineral.

By annealing limonite releases water so dehydrated. To determine whether an ocher- colored rock or a potential color earth contains limonite, keeping a sample over a gas flame until it begins to glow red. Has it changed color after cooling into the Red or Purple, it was limonite. This also explains that many yellow tone (eg Terracotta ) result after burning reddish pottery or brick goods. On the same effect based pigments burnt ocher, burnt sienna or burnt umber.

Education and Locations

Limonite is a component of ferruginous sedimentary rocks. These are called stones or iron obsolete as iron limestone. Examples of such rocks are bog iron ore, oolitic iron stones, Minette, Debris iron ore and bean ore.

Furthermore comes limonite found in secondary deposits ( deposits that formed by the weathering of primary minerals). Often it is found as a weathering product of iron-containing minerals ( olivine, pyroxene, amphibole, biotite, but also of magnetite) in the mafic volcanic rocks such as basalt or melaphyre and felsic igneous rocks such as diorite and in granite. In everyday life, we encounter limonite especially as rust on iron objects.

Limonite occurs in various formations on: brown iron (as tropfige, low one or slag -like variety - yellow-brown to almost black), earthy limonite ( yellow-brown, not to be confused to black with manganese dioxide, manganese oxide ). Sedimentary deposits are often made (light fawn to dark rusty brown, a limonite - impregnated limestone) from Eisenkalk and highly enriched with limonite Latvians layers, which are formed either as a firm, solid brown iron ore or as Latvians. The latter are obtained as earth colors ( ocher pigment such and Siena). Ochre is a powder-like form of the crystalline weathering Limonits that was traded as a color earth as Umbra and is also known in the mining Brauneisenmulm. It is also found in the weathering zone basic accompanied veins (eg in the " gossan " of Kupfer-/Zinkgänge of the Ore Mountains ).

In addition to magnetite and hematite is limonite is the most important iron ore, which today won yet in many countries in large open pit mines. FeO (OH) is the final product, which is formed at the iron rusts.

Known localities in Germany are mainly Auerbach in der Oberpfalz and Sulzbach- Rosenberg, Bavaria, Eschweiler ( in Korkus and Propsteier Forest) in North Rhine -Westphalia and Kamsdorf ( in Saalfeld ), Brotterode - Trusetal ( Laudenbach ) Atterode ( Stahlberg, High Blade ) and Albrecht ( the "old field") in Thuringia.

History

In ancient times, played brown iron ore to iron production is less important than hematite, which was better verhüttbar in the old racing fires. Only with the introduction of the piece, blue and High ovens in the 16th century began the flourishing of brown iron ore.

However, in his capacity as a proportion of the earth pigments he is one of the earliest materials used by man and can be detected in stone age cave paintings and rock art.

Limoniteinlagerungen in rocks

The minerals of the Limonitkomplexes are a natural coloring component and often held by many rocks in a very finely divided form. In many sandstones they cause yellowish to reddish brown color. In carbonate rocks yellow tints are available in all shades thereby also frequently causes. Limonite and related minerals are an important but not the only yellow -sounding rock constituent.

Of particular importance is the circumstance where limonite and other iron minerals in building and decorative rocks are present in finely divided form so that they can not be seen with the eye, but produce by later environmental impact or further processing a subsequent yellowing. For example, this phenomenon occurs in some granites and certain varieties of Carrara marble, which after laying in strongly alkaline adhesives or by the action of atmospheric agents significant discoloration in different sized areas. As is usual with all other materials, is to clarify the suitability of the rock for the specific application by those skilled in the context of such phenomena.