Hematite - AbsoluteAstronomy.com

Hematite, also spelled as haematite, is the mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

form of iron(III) oxide

Iron(III) oxide

Iron oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron oxide , which is rare, and iron oxide , which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main...

(Fe₂O₃), one of several iron oxide

Iron oxide

Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...

s. Hematite crystallizes in the rhombohedral system, and it has the same crystal

Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

structure as ilmenite

Ilmenite

Ilmenite is a weakly magnetic titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite....

and corundum

Corundum

Corundum is a crystalline form of aluminium oxide with traces of iron, titanium and chromium. It is a rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red...

. Hematite and ilmenite form a complete solid solution

Solid solution

A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase...

at temperatures above 950 °C.

Hematite is a mineral, colored black to steel or silver-gray, brown to reddish brown, or red. It is mined

Mining

Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...

as the main ore of iron. Varieties include kidney ore, martite (pseudomorph

Pseudomorph

In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form , resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another...

s after magnetite

Magnetite

Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...

), iron rose and specularite (specular hematite). While the forms of hematite vary, they all have a rust-red streak. Hematite is harder than pure iron, but much more brittle. Maghemite

Maghemite

Maghemite is a member of the family of iron oxides. It has the same structure as magnetite, that is, it is spinel ferrite and is also ferrimagnetic.Maghemite can be considered as an Fe-deficient magnetite with formula...

is a hematite- and magnetite

Magnetite

-related oxide mineral.

Huge deposits of hematite are found in banded iron formation

Banded iron formation

Banded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers of iron oxides, either magnetite or hematite , alternating with bands of iron-poor shale and chert...

s. Grey hematite is typically found in places where there has been standing water or mineral hot spring

Hot spring

A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. There are geothermal hot springs in many locations all over the crust of the earth.-Definitions:...

s, such as those in Yellowstone National Park

Yellowstone National Park

Yellowstone National Park, established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872, is a national park located primarily in the U.S. state of Wyoming, although it also extends into Montana and Idaho...

in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. The mineral can precipitate

Precipitation (chemistry)

Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...

out of water and collect in layers at the bottom of a lake, spring, or other standing water. Hematite can also occur without water, however, usually as the result of volcanic

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

activity.

Clay

Clay

Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

-sized hematite crystals can also occur as a secondary mineral formed by weathering

Weathering

Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

processes in soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

, and along with other iron oxides or oxyhydroxides such as goethite

Goethite

Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...

, is responsible for the red color of many tropical, ancient, or otherwise highly weathered soils.

Etymology and history

The name hematite is derived from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

word for blood αἷμα haima because hematite can be red, as in rouge

Iron(III) oxide

, a powdered form of hematite. The color of hematite lends it well in use as a pigment

Pigment

A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

. The English name of the stone is derived from Middle French

Middle French

Middle French is a historical division of the French language that covers the period from 1340 to 1611. It is a period of transition during which:...

: Hématite Pierre, which was imported from Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

: Lapis Hæmatites, which originated from Ancient Greek

Ancient Greek

Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

: αἱματίτης λίθος (haimatitēs lithos, “blood-red stone”).

Ochre is a clay that is colored by varying amounts of hematite, varying between 20% and 70%. Red ochre contains unhydrated hematite, whereas yellow ochre contains hydrate

Hydrate

Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....

d hematite (Fe

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

₂O

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

₃ • H

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

₂O

Oxygen

). The principal use of ochre is for tinting with a permanent color.

The red chalk winning of this mineral was one of the earliest in history of mankind. The powdery mineral was first used 164,000 years ago by the Pinnacle-Point man obviously for social differentiation. Hematite residues are also found in old graveyards from 80,000 years ago. Near Rydno in Poland

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

and Lovas in Hungary

Hungary

Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

, palaeolitic red chalk mines have been found that are from 5000 BC, belonging to the Linear Pottery culture

Linear Pottery culture

The Linear Pottery culture is a major archaeological horizon of the European Neolithic, flourishing ca. 5500–4500 BC.It is abbreviated as LBK , is also known as the Linear Band Ware, Linear Ware, Linear Ceramics or Incised Ware culture, and falls within the Danubian I culture of V...

at the Upper Rhine

Upper Rhine

The Upper Rhine is the section of the Rhine in the Upper Rhine Plain between Basel, Switzerland and Bingen, Germany. The river is marked by Rhine-kilometers 170 to 529 ....

.

Rich deposits of hematite have been found on the island of Elba

Elba

Elba is a Mediterranean island in Tuscany, Italy, from the coastal town of Piombino. The largest island of the Tuscan Archipelago, Elba is also part of the National Park of the Tuscan Archipelago and the third largest island in Italy after Sicily and Sardinia...

that have been mined till the time of the Etruscans.

Jewelry

Hematite's popularity in jewelry was at its highest in Europe during the Victorian era

Victorian era

The Victorian era of British history was the period of Queen Victoria's reign from 20 June 1837 until her death on 22 January 1901. It was a long period of peace, prosperity, refined sensibilities and national self-confidence...

, and has since seen a strong resurgence in North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, especially in the western United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. Certain types of hematite or iron oxide rich clay, especially Armenian bole

Armenian bole

Armenian bole, also known as bolus armenus or bole armoniac, is an earthy clay, usually red, native to Armenia. It is red due to the presence of iron oxide; the clay also contains hydrous silicates of aluminum and possibly magnesium.-Uses:...

has been used in gilding

Gilding

The term gilding covers a number of decorative techniques for applying fine gold leaf or powder to solid surfaces such as wood, stone, or metal to give a thin coating of gold. A gilded object is described as "gilt"...

. Hematite is also used in art such as intaglio engraved gems. Hematine

Hematine

Hematine is an artificial magnetic material. Hematine is widely used in jewelry....

is a synthetic material sold as magnetic hematite.

Magnetism

Hematite is an antiferromagnetic material below the Morin transition

Morin transition

The Morin transition is a magnetic phase transition in α-Fe2O3 hematite where the antiferromagnetic ordering is reorganized from being aligned perpendicular to the c-axis to be aligned parallel to the c-axis below TM....

at 250 K, and a canted antiferromagnet or weakly ferromagnetic above the Morin transition and below its Néel temperature

Néel temperature

The Néel temperature or magnetic ordering temperature , TN, is the temperature above which an antiferromagnetic material becomes paramagnetic—that is, the thermal energy becomes large enough to destroy the macroscopic magnetic ordering within the material....

at 948 K, above which it is paramagnetic.

The magnetic structure of a-hematite was the subject of considerable discussion and debate in the 1950s because it appeared to be ferromagnetic with a Curie temperature of around 1000 K, but with an extremely tiny moment (0.002 µ_B). Adding to the surprise was a transition with a decrease in temperature at around 260 K to a phase with no net magnetic moment. It was shown that the system is essentially antiferromagnetic but that the low symmetry of the cation sites allows spin–orbit coupling to cause canting of the moments when they are in the plane perpendicular to the c axis. The disappearance of the moment with a decrease in temperature at 260 K is caused by a change in the anisotropy

Anisotropy

Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies identical properties in all directions. It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties An example of anisotropy is the light...

which causes the moments to align along the c axis. In this configuration, spin canting does not reduce the energy.

Hematite is part of a complex solid solution oxyhydroxide system having various degrees of water, hydroxyl group, and vacancy substitutions that affect the mineral's magnetic and crystal chemical properties. Two other end-members are referred to as protohematite and hydrohematite.

Iron from mine tailings

Hematite is present in the waste tailings

Tailings

Tailings, also called mine dumps, slimes, tails, leach residue, or slickens, are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore...

of iron mines. A recently developed process, magnetation

Magnetation (iron ore)

Magnetation is a term referring to the processing of iron ore tailings, the waste product of iron ore mines, to recover hematite. Crushed mine tailings are mixed with water to create a slurry; the slurry is then pumped through magnetic separation chambers to extract hematite...

, uses huge magnets to glean waste hematite from old mine tailings in Minnesota

Minnesota

Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

's vast Mesabi Range

Mesabi Range

The Mesabi Iron Range is a vast deposit of iron ore and the largest of four major iron ranges in the region collectively known as the Iron Range of Minnesota. Discovered in 1866, it is the chief deposit of iron ore in the United States. The deposit is located in northeast Minnesota, largely in...

iron district.

Discovery on Mars

The spectral signature of hematite was seen on the planet Mars

Mars

Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

by the infrared spectrometer

Spectrometer

A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...

on the NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

Mars Global Surveyor

The Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on 2...

("MGS") and 2001 Mars Odyssey

2001 Mars Odyssey

2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectrometers and electronic imagers to hunt for evidence of past or...

spacecraft in orbit around Mars. The mineral was seen in abundance at two sites on the planet, the Terra Meridiani site, near the Martian equator at 0° longitude, and the second site Aram Chaos

Aram Chaos

Aram Chaos, centered at 2.6°N, 21.5°W, comprises a heavily eroded impact crater on the planet Mars. It lies at the eastern end of the large canyon Valles Marineris and close to Ares Vallis. Various geological processes have reduced it to a circular area of chaotic terrain...

near the Valles Marineris

Valles Marineris

Valles Marineris is a system of canyons that runs along the Martian surface east of the Tharsis region...

. Several other sites also showed hematite, e.g., Aureum Chaos. Because terrestrial hematite is typically a mineral formed in aqueous environments, or by aqueous alteration, this detection was scientifically interesting enough that the second of the two Mars Exploration Rover

Mars Exploration Rover

NASA's Mars Exploration Rover Mission is an ongoing robotic space mission involving two rovers, Spirit and Opportunity, exploring the planet Mars...

s was targeted to a site in the Terra Meridiani region designated Meridiani Planum

Meridiani Planum

Meridiani Planum is a plain located 2 degrees south of Mars' equator , in the westernmost portion of Terra Meridiani. It hosts a rare occurrence of gray crystalline hematite...

. In-situ investigations by the Opportunity rover

Opportunity rover

Opportunity, MER-B , is a robotic rover on the planet Mars, active since 2004. It is the remaining rover in NASA's ongoing Mars Exploration Rover Mission...

showed a significant amount of hematite, much of it in the form of small spherules

Martian spherules

Martian spherules are the abundant spherical hematite inclusions discovered by the Mars rover Opportunity at Meridiani Planum on the planet Mars...

that were informally named "blueberries" by the science team. Analysis indicates that these spherules are apparently concretion

Concretion

A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity . Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and crescere meaning 'to grow'...

s formed from a water solution.
"Knowing just how the hematite on Mars was formed will help us characterize the past environment and determine whether that environment was favorable for life," .. "One big question, of course, is whether life ever started on Mars. This mission probably won't tell us that, but it may well lead to future mission that can answer that question."

External links

Abandoned Mine Research.
Mars spheres image.
Mars trench image showing a shiny texture of half-buried spheres (dark line is equipment shadow)
Florence Mine, Cumbria, UK.
MineralData.org