Hematite
General
Category	Oxide mineral
Chemical formula	iron(III) oxide, Fe2O3, α-Fe2O3
Identification
Color	Metallic grey to earthy red tones
Crystal habit	Tabular to thick crystals
Crystal system	Hexagonal (rhombohedral)
Cleavage	None
Fracture	Uneven to sub-conchoidal
Mohs Scale hardness	5. A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Iron(III oxide —also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply Rust —is In Mineralogy, shape and size give rise to descriptive terms applied to the typical appearance or habit of Crystals The many terms used by mineralogists A crystal system is a category of Space groups which characterize Symmetry of structures in three dimensions with Translational symmetry in three directions Regular hexagon The internal Angles of a regular hexagon (one where all sides and all angles are equal are all 120 ° and the hexagon has 720 degrees Cleavage, in Mineralogy, is the tendency of crystalline materials to split along definite planes creating smooth surfaces of which there are several named types In the field of Mineralogy, fracture is a term used to describe the shape and texture of the surface formed when a Mineral is broken The Mohs scale of mineral hardness characterizes the scratch resistance of various Minerals through the ability of a harder material to scratch a softer material 5 - 6. 5
Luster	Metallic to splendent
Refractive index	Opaque
Pleochroism	None
Streak	Bright red to dark red
Specific gravity	4. Lustre (or luster) is a description of the way light interacts with the surface of a Crystal, rock, or Mineral. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium Pleochroism is an Optical phenomenon in which grains of a rock appear to be different colors when observed at different angles under a Petrographic microscope. The streak (also called powder color) of a Mineral is the Color of the powder produced when it is dragged across an unweathered surface Specific gravity is defined as the ratio of the Density of a given solid or liquid substance to the density of water at a specific temperature and pressure typically 9 - 5. 3
References	[1][2]

Hematite, also spelled hæmatite, is the mineral form of Iron(III) oxide (Fe₂O₃), one of several iron oxides. American and British English spelling differences are one aspect of American and British English differences. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Iron(III oxide —also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply Rust —is Altogether there are sixteen known Iron Oxides and oxyhydroxides Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and as corundum. In Crystallography, the rhombohedral (or trigonal) Crystal system is one of the seven lattice point groups named after the two-dimensional In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Ilmenite is a weakly magnetic titanium-iron oxide Mineral which is iron-black or steel-gray Corundum (from Tamil kurundam குருந்தம் or kuruvindam குருவிந்தம் is a Crystalline form of Hematite and ilmenite form a complete solid solution at temperatures above 950°C. A solid solution is a Solid - state Solution of one or more solutes in a Solvent.

Hematite (kidney ore) from Michigan (unknown scale)

Hematite is a mineral, colored black to steel or silver-gray, brown to reddish brown, or red. It is mined as the main ore of iron. Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body Iron ores are rocks and Minerals from which Metallic Iron can be economically extracted Varieties include kidney ore, martite (pseudomorphs after magnetite), iron rose and specularite (specular hematite). In Geology, a pseudomorph is a Mineral compound resulting from a substitution process in which the appearance and dimensions remain constant but the mineral which Magnetite is not to be confused with Magnesite or Maghemite. Magnetite is a ferrimagnetic Mineral with chemical While the forms of hematite vary, they all have a rust-red streak. Hematite is harder than pure iron, but much more brittle.

Huge deposits of hematite are found in banded iron formations. Banded iron formations (also known as banded ironstone formations or BIF s are a distinctive type of rock often found in primordial ( Precambrian) Sedimentary Grey hematite is typically found in places where there has been standing water or mineral hot springs, such as those in Yellowstone. A hot spring is a spring that is produced by the emergence of geothermally heated Groundwater from the earth's crust. The mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water. Precipitation is the formation of a Solid in a Solution during a Chemical reaction. Hematite can also occur without water, however, usually as the result of volcanic activity. Plate tectonics and hotspots Divergent plate boundaries At the

Clay-sized hematite crystals can also occur as a secondary mineral formed by weathering processes in soil, and along with other iron oxides or oxyhydroxides such as goethite, is responsible for the red color of many tropical, ancient, or otherwise highly weathered soils. Clay is a naturally occurring material composed primarily of fine-grained Minerals which show plasticity through a variable range of Water content, and Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. Soil, often typeset as SOiL, is a four piece rock band from Chicago Illinois United States founded by Shaun Glass Tom Schofield Tim King and Adam Zadel Goethite, named after the German Polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low temperature environments The Tropics are centered on the Equator and limited in Latitude by the Tropic of Cancer in the northern hemisphere at approximately 23°26' (23

Rainbow Hematite from Brazil (unknown scale)

Hematite in Scanning Electron Microscope ("SEM"), magnification 20x

Hematite in SEM, magnification 100x

Hematite in SEM, magnification 200x

Good specimens of hematite come from England, Mexico, Brazil, Australia and the Lake Superior region of the United States and Canada. The scanning electron microscope ( SEM) is a type of Electron microscope that images the sample surface by scanning it with a high-energy beam of Electrons England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland The United Mexican States ( or commonly Mexico (ˈmɛksɪkoʊ () is a federal constitutional Republic in North America. |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld For a topic outline on this subject see List of basic Australia topics. Lake Superior is the largest of the five Great Lakes of North America. The United States of America —commonly referred to as the Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page

Ochre

Main article: Ochre

The name hematite is derived from the Greek word for blood (haima) because hematite can be red, as in rouge, a powdered form of hematite. Ochre or Ocher (pronounced /'əʊkə(r/ from the Greek ὠχρός yellow is a Color, usually described as golden - Yellow Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Iron(III oxide —also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply Rust —is The color of hematite lends it well in use as a pigment. For the drug referred to as "pigment" see Black tar heroin.

Ochre is a clay that is colored by varying amounts of hematite, varying between 20% and 70% ^[3]. Red ochre contains unhydrated hematite, whereas yellow ochre contains hydrated hematite (Fe₂O₃ • H₂O). Red ochre and yellow ochre (pronounced /'əʊkə/ from the Greek ὄχρος yellow are Pigments made from naturally tinted Clay. Red ochre and yellow ochre (pronounced /'əʊkə/ from the Greek ὄχρος yellow are Pigments made from naturally tinted Clay. Hydrate is a term used in Inorganic chemistry and Organic chemistry to indicate that a substance contains Water. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the The principal use of ochre is for tinting with a permanent color^[3].

Magnetism

Hematite is an antiferromagnetic material below the Morin transition at 260 K, and a canted antiferromagnet or weakly ferromagnetic [1] above the Morin transition and below its Néel temperature at 948K, above which it is paramagnetic. In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules usuallyrelated to the spins of Electrons align in a regular pattern with neighboring The Morin transition is a magnetic Phase transition in α-Fe2O3 Hematite where the Antiferromagnetic ordering is reorganized from Ferromagnetism is the basic mechanism by which certain materials (such as Iron) form Permanent magnets and/or exhibit strong interactions with Magnets it The Néel temperature, TN is the Temperature at which an Antiferromagnetic material becomes Paramagnetic &mdash that is the thermal energy Paramagnetism is a form of magnetism which occurs only in the presence of an externally applied magnetic field

Hematite specimen showing well-developed botryoidal structure for which this mineral is well-known. (Unknown scale)

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. 002mB). Adding to the surprise was a transition with a decrease in temperature at around 260 K to a phase with no net magnetic moment.

Dzialoshinksi and later Moriya showed 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 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. ^[4] Two other end-members are referred to as protohematite and hydrohematite.

Hematite on Mars

Image mosaic from the Mars Exploration Rover Microscopic Imager shows Hematite spherules partly embedded in rock at the Opportunity landing site. Martian spherules (also known as blueberries due to their blue hue in false-color images released by NASA are the abundant spherical hematite inclusions discovered by the (Scale: image is approximately 5 cm (2 in) across)

The spectral signature of hematite was seen on the planet Mars by the infrared spectrometer on the NASA Mars Global Surveyor ("MGS") and 2001 Mars Odyssey spacecraft in orbit around Mars ^[5]. A spectrometer is an Optical instrument used to measure properties of Light over a specific portion of the Electromagnetic spectrum, typically used The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The Mars Global Surveyor ( MGS) was a US Spacecraft developed by NASA and the Jet Propulsion Laboratory and launched 2001 Mars Odyssey is a Robotic spacecraft Orbiting the planet Mars. The mineral was seen in abundance at two sites^[6]. on the planet, the Terra Meridiani site, near the Martian equator at 0° longitude, and the second site Aram Chaos near the Valles Marineris ^[7]. Sinus Meridiani is a feature name for an Albedo feature on Mars stretching east-west just south of that planet's Equator. Aram Chaos, centered at 26°N 215°W is a heavily eroded Impact crater on the planet Mars. Valles Marineris ( Latin for Mariner Valleys, named after the Mariner 9 Mars orbiter Several other sites also showed hematite, e. g. , Aureum Chaos ^[8]. 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 Rovers was targeted to a site in the Terra Meridiani region designated Meridiani Planum. NASA 's Mars Exploration Rover ( MER) Mission is an ongoing robotic mission of exploring Mars, that began in 2003 with the sending of Meridiani Planum is a plain located 2 degrees south of Mars ' equator (centered at) in the westernmost portion of Terra Meridiani. In-situ investigations by the Opportunity rover showed a significant amount of hematite, much of it in the form of small spherules that were informally tagged by the science team "blueberries" (a term which is somewhat confusing, since in spectrally-correct color images they are, in fact, silver-grey in color). MER-B ( Mars Exploration Rover - B) known as Opportunity, is the second of the two rovers of NASA 's Mars Exploration Martian spherules (also known as blueberries due to their blue hue in false-color images released by NASA are the abundant spherical hematite inclusions discovered by the Analysis indicates that these spherules are apparently concretions formed from a water solution. A concretion is a volume of Sedimentary rock in which a Mineral cement fills the porosity (i

Jewelry

Hematite's popularity in jewelry was at its highest in Europe during the Victorian era, while in the last 50 years it has been popular in North America, especially in the western United States where it is found in jewelry and art created by Native Americans. Culture The Victorian fascination with novelty resulted in a deep interest in the relationship between modernity and cultural continuities The United States of America —commonly referred to as the Native Americans in the United States are the indigenous peoples from the regions of North America now encompassed by the continental United States Care should be taken in handling hematite items due to the material's susceptibility to damage.

See also

Hematite carving, 5 cm (2 in) long.

• Iron ore
• List of minerals
• Wüstite
• Magnetite
• Mineral redox buffer
• Scientific information from the Mars Exploration Rover mission

References

• Martite - Mindat w/ location data
• Iron rose - Mindat w/ locations

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