What is the formula for hematite

Hematite, Roteisenstein
According to the Greek word haima ("Blood")
formula
Substance group
colour
Line
shine
transparency
Hardness (Mohs)
density
Cleavage
fracture

Crystal system
Crystal class
Fe2O3, Turgit: Fe2O3 • nH2O
Oxides
gray, blue-black, red
blood red, brown
Metallic gloss or matt
opaque (compact)
5,5 – 6,5
4.9-5.3 g / cm³
no
uneven, scalloped, scaly

trigonal
ditrigonal-scalenohedral

Iron ore weathered from the Cleeberg in Hesse

Glass head from Igleta Ighoud in Morocco

Hematite pseudomorphic from Magnetite, Utah
Hematite, N'Chwaning Mine II, Kalahari, South Africa

Eisenrose from Obergoms, Switzerland

Hematite from Elba Island, Italy
Hematite extensive with rutile, Cavradi gorge

Hematite iron rose from Ouro Preto, Brazil
properties

Pure hematite is a blue-black glossy, opaque mineral that is reddish translucent only in the finest flakes. The mineral can tarnish in the air. The black hematite weathers in the humidity to red hematite. It can be distinguished from other black ores by the blood-red color of the streak. In powdered form, the mineral is slowly soluble in hydrochloric acid. It cannot be melted in front of the soldering tube. Natural hematite itself is not ferromagnetic, but it can be magnetized: Pieces that are commercially available as "magnetic iron ore" usually do not contain magnetite, but consist of subsequently magnetized hematite.


Varieties and pseudomorphs

Occasionally one calls the hematite in reference to the high metal gloss also specularite, which refers to the Latin word speculum ("Spiegel") refers. Quartz that is streaked with hematite is called Tiger Travel designated. Hematite is a component of the red ocher, which is required as a color pigment. As Turgite a mixture of hematite and goethite is called. It arises from the weathering of the goethite. The Maghemite on the other hand, is an independent mineral, which consists of the γ-modification of iron (III) oxide and crystallizes in the cubic crystal system. Glass head is a spherical-kidney hematite.

The hematite colors numerous other minerals such as calcite or quartz red. Pseudomorphoses are known from the transformation of calcite, dolomite or magnetite into hematite.


Crystal forms and growth

Hematite crystallizes according to the trigonal system: basic pinacoids, prisms, rhombohedra, dipyramids and scalenohedra build up the crystal forms in many combinations. The habitus is often pseudo-hexagonal. Penetration twins also occur. The miners used to refer to the shiny hematite crystals as Iron luster. Leafy or scaly aggregates are called Iron mica. Hematite also occurs like a wire to needle-like, coarse, massive or granular. Earthy or loose aggregates are broken down as "red chalk" or "red iron ocher" for painting.

Tabular crystals that are arranged as a rosette are called Iron rose designated. The first were found in 1810 at the Passo di Lucendro in the Swiss canton of Ticino. The iron roses from the alpine fissures often also contain titanium dioxide or are penetrated by rutile needles. Foreign admixtures with titanium lead to a black line color. The thick tabular, extensive haematites from the Swiss Cavradi Gorge or from the Chollergraben in the Binn valley are not iron roses. Red-brown rutile crystals often grow on these aggregates.


history

Iron as a metal was already known in antiquity. The Iron Age began after the Bronze Age around 1400 BC. The Hittites, a tribe in the Middle East, are considered to be the inventors of iron extraction from iron ore. Colored earths that are colored red by hematite are the oldest coloring agents known to mankind. The cave painters used these to create their works of art. The name of the hematite refers to the color and is after the Greek word haima ("Blood") named. The term haimatites lithos means something like "blood stone". The term was mentioned by the Greek natural scientist and philosopher Theophrast around 300 BC. The Roman scholar Pliny the Elder also used the term.

Iron ore mining on the island of Elba can be traced back to the Etruscans in the 7th century BC. The Romans also mined hematite on Elba. The most productive site is at Rio Marina. The hematite occurs there in a very high purity. Pliny already pointed out the environmental consequences of intensive mining of the ore on Elba and feared for the forests and the wood resources on the island. Wood was the raw material for charcoal, which was necessary for iron production. After the resources on Elba were no longer sufficient for the Roman Empire, the Romans looked for other sources. They took the ore from their provinces and from Africa. At some point the fuel on Elba also dried up. In the 19th century, the ironworks for processing the ore were located in Corsica or on Europe's coastal regions, where there were still forests. In the 20th century pyrite was mined on Elba. The iron ore production was stopped in 1980.


Occurrence

In the early history of the earth, iron came to the earth through countless meteorite impacts. In the ancient seas, iron oxidized to form iron oxides, which were deposited in the sediment. This is how the iron ore deposits came about. There is a historical deposit on the island of Elba in Italy. In Germany, for example, the coveted ore was extracted in the iron ore mines of the Lahn- and Dillmulde in Hesse or in the Ore Mountains. Minable ore deposits can be found today in China, Australia, Brazil, India, Russia and the Ukraine. Hematite has also been detected on Mars. This is evidence that there was once a great deal of water on Mars.

For example, the Swiss hematite aggregates from the Cavradi Gorge, if they are studded with rutile crystals, or the iron roses from the Swiss Aar massif, such as those found near Obergoms in Valais, are popular with collectors. However, the largest iron roses do not come from Switzerland, but from Ouro Preto in Brazil.


use

Red iron ore is an important ore for the extraction of iron in the blast furnace process. Iron oxide red is used as a permanent pigment for anti-rust paints, paints and for coloring ceramics. However, synthetically produced and pure iron (III) oxide is preferred. Due to its magnetizability, iron (III) oxide is suitable as a carrier material on audio tapes, which are still used today in professional music productions. Hematite is also a popular material for making gemstones.



Wire-like hematite from Nickenich in the Eifel

Hematite pseudomorphic after Calcite, Laurion

Red ocher from Spain

"Tiger iron" heart: hematite, limonite, quartz