Limonite (3) Raw Minerals Stones Rocks Collecting

Description

Origin : Italy (Trentino)

Limonite 61-80 gr - cm 5-8 Raw Minerals Stones Rocks for Collection.

Limonite is a hydrated iron oxide, FeO(OH)·nH2O, which is formed by the decay of other iron minerals from whose deposits it forms the cap.
It is not a mineralogical species in its own right, but the term is used to indicate unidentified pseudomorphic masses of iron oxides and hydroxides without visible crystals, usually consisting of goethite, but also maghemite, hematite, lepidocrocite, hisingerite, picticite and others minerals of the jarosite group. Limonite is therefore a mixture of minerals and amorphous materials, it forms earthy, concretionary, mamellar and stalactitic masses, and fibrous and radiant aggregates. Frequently pseudomorphic, on pyrite and other iron ores. Due to its amorphous nature and occurrence in hydrated areas, limonite often occurs as clay or mud.
For this reason, the mineral has no codes according to modern classifications and has a variable crystalline shape, which in the individual crystals generally reflects that of the iron ore from which it was formed.
It forms as a secondary mineral in the oxidation zone of iron deposits; it is also formed by precipitation in marine, fresh and marshy waters.
Limonite usually forms from the hydration of hematite and magnetite, oxidation and hydration of iron-rich sulfide minerals, and chemical weathering of other iron-rich minerals such as olivine, pyroxenes, amphiboles and biotite.
Limonite is relatively dense with a specific gravity ranging from 2.7 to 4.3. Hardness is variable, but generally in the range of Mohs scale values ​​between 4 and 5.5.
The earthy masses of limonite have colors ranging from tan to brown, or yellowish brown, so-called ocher, and are used as dyes.
One of the earliest uses was as a pigment. The yellow form produced yellow ochre, while the darker forms produced more earthy tones. Roasting limonite partially changed it to hematite, yielding red ochres, burnt umber, and sienna.