Hematite

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Hematite
WLA hmns Hematite.jpg
Brazilian trigonal hematite crystal
General
Category Oxide minerals
Formula
(repeating unit)
iron(III) oxide, Fe2O3, α-Fe2O3 [1]
Strunz classification 4.CB.05
Dana classification4.3.1.2
Crystal system Trigonal
Crystal class Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
Space group R3c
Unit cell a = 5.038(2) Å;
c = 13.772(12) Å; Z = 6
Identification
ColorMetallic gray, dull to bright red
Crystal habit Tabular to thick crystals; micaceous or platy, commonly in rosettes; radiating fibrous, reniform, botryoidal or stalactitic masses, columnar; earthy, granular, oolitic
Twinning Penetration and lamellar
Cleavage None, may show partings on {0001} and {1011}
Fracture Uneven to sub-conchoidal
Tenacity Brittle
Mohs scale hardness5.5–6.5
Luster Metallic to splendent
Streak Bright red to dark red
Diaphaneity Opaque
Specific gravity 5.26
Density 5.3
Optical propertiesUniaxial (-)
Refractive index nω = 3.150–3.220, nε = 2.870–2.940
Birefringence δ = 0.280
Pleochroism O = brownish red; E = yellowish red
References [2] [3] [4]

Hematite, also spelled as haematite, is the mineral form of iron(III) oxide (Fe2O3), one of several iron oxides. It is the oldest known iron oxide mineral that has ever formed on Earth, and is widespread in rocks and soils. [5] Hematite crystallizes in the rhombohedral lattice system, and it has the same crystal structure as ilmenite and corundum. Hematite and ilmenite form a complete solid solution at temperatures above 950 °C (1,740 °F).

Mineral Element or chemical compound that is normally crystalline and that has been formed as a result of geological processes

A mineral is, broadly speaking, a solid chemical compound that occurs naturally in pure form. A rock may consist of a single mineral, or may be an aggregate of two or more different minerals, spacially segregated into distinct phases. Compounds that occur only in living beings are usually excluded, but some minerals are often biogenic and/or are organic compounds in the sense of chemistry. Moreover, living beings often synthesize inorganic minerals that also occur in rocks.

Iron(III) oxide chemical compound

Iron(III) 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(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main source of iron for the steel industry. Fe2O3 is readily attacked by acids. Iron(III) oxide is often called rust, and to some extent this label is useful, because rust shares several properties and has a similar composition. To a chemist, rust is considered an ill-defined material, described as hydrated ferric oxide.

Iron oxide chemical compound composed of iron and oxygen

Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.

Contents

Hematite is colored black to steel or silver-gray, brown to reddish brown, or red. It is mined as the main ore of iron. Varieties include kidney ore, martite (pseudomorphs after magnetite), 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 is a hematite- and magnetite-related oxide mineral.

Mining The extraction of valuable minerals or other geological materials from the earth

Mining is the extraction of valuable minerals or other geological materials from the earth, usually from an ore body, lode, vein, seam, reef or placer deposit. These deposits form a mineralized package that is of economic interest to the miner.

Pseudomorph mineral or mineral compound that appears in an atypical form

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. The name literally means "false form".

Magnetite iron ore mineral

Magnetite is a rock mineral and one of the main iron ores, with the chemical formula Fe3O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. It is the most magnetic of all the naturally-occurring minerals on Earth. Naturally-magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, which is how ancient peoples first discovered the property of magnetism. Today it is mined as iron ore.

A microscopic picture of hematite Hematite - Titanomagnitite.jpg
A microscopic picture of hematite

Huge deposits of hematite are found in banded iron formations. Gray hematite is typically found in places that can have still standing water or mineral hot springs, such as those in Yellowstone National Park in North America. The mineral can precipitate 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 activity.

Banded iron formation Distinctive layered units of iron-rich sedimentary rock that are almost always of Precambrian age

Banded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age.

Hot spring spring produced by the emergence of geothermally heated groundwater

A hot spring is a spring produced by the emergence of geothermally heated groundwater that rises from the Earth's crust. While some of these springs contain water that is a safe temperature for bathing, others are so hot that immersion can result in injury or death.

Yellowstone National Park first national park in the world, located in the US states Wyoming, Montana and Idaho

Yellowstone National Park is an American national park located in Wyoming, Montana, and Idaho. It was established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872. Yellowstone was the first national park in the U.S. and is also widely held to be the first national park in the world. The park is known for its wildlife and its many geothermal features, especially Old Faithful geyser, one of its most popular features. It has many types of ecosystems, but the subalpine forest is the most abundant. It is part of the South Central Rockies forests ecoregion.

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 A finely-grained natural rock or soil material that combines one or more clay minerals

Clay is a finely-grained natural rock or soil material that combines one or more clay minerals with possible traces of quartz (SiO2), metal oxides (Al2O3, MgO etc.) and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to particle size and geometry as well as water content, and become hard, brittle and non–plastic upon drying or firing. Depending on the soil's content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red.

Weathering Breaking down of rocks, soil and minerals as well as artificial materials through contact with the Earths atmosphere, biota and waters

Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, water, and biological organisms. Weathering occurs in situ, that is, in the same place, with little or no movement, and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind, waves and gravity and then being transported and deposited in other locations.

Soil mixture of organic matter, minerals, gases, liquids, and organisms that together support life

Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Earth's body of soil, called the pedosphere, has four important functions:

Crystal structure of hematite Hematite structure.jpg
Crystal structure of hematite

Etymology and history

The name hematite is derived from the Greek word for blood αἷμα haima, due to the red coloration found in some varieties of hematite [5] . The color of hematite lends itself to use as a pigment. The English name of the stone is derived from Middle French: Hématite Pierre, which was imported from Latin: Lapis Hæmatites around the 15th century, which originated from Ancient Greek: αἱματίτης λίθος (haimatitēs lithos, "blood-red stone").

Greek language language spoken in Greece, Cyprus and Southern Albania

Greek is an independent branch of the Indo-European family of languages, native to Greece, Cyprus and other parts of the Eastern Mediterranean and the Black Sea. It has the longest documented history of any living Indo-European language, spanning more than 3000 years of written records. Its writing system has been the Greek alphabet for the major part of its history; other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic, and many other writing systems.

Pigment material that changes the color of reflected or transmitted light

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. Most materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have special properties that make them useful for coloring other materials. A pigment must have a high tinting strength relative to the materials it colors. It must be stable in solid form at ambient temperatures.

Middle French is a historical division of the French language that covers the period from the 14th to the early 17th centuries. It is a period of transition during which:

Ochre is a clay that is colored by varying amounts of hematite, varying between 20% and 70%. [6] Red ochre contains unhydrated hematite, whereas yellow ochre contains hydrated hematite (Fe 2 O 3H 2 O). The principal use of ochre is for tinting with a permanent color. [6]

Ochre painting material and color

Ochre or ocher is a natural clay earth pigment which is a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced by this pigment, especially a light brownish-yellow. A variant of ochre containing a large amount of hematite, or dehydrated iron oxide, has a reddish tint known as "red ochre".

In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understood.

Oxygen Chemical element with atomic number 8

Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O
2
. Diatomic oxygen gas constitutes 20.8% of the Earth's atmosphere. As compounds including oxides, the element makes up almost half of the Earth's crust.

The red chalk writing of this mineral was one of the earliest in the history of humans. The powdery mineral was first used 164,000 years ago by the Pinnacle-Point man possibly for social purposes. [7] Hematite residues are also found in graves from 80,000 years ago. Near Rydno in Poland and Lovas in Hungary red chalk mines have been found that are from 5000 BC, belonging to the Linear Pottery culture at the Upper Rhine. [8]

Rich deposits of hematite have been found on the island of Elba that have been mined since the time of the Etruscans.

Magnetism

Hematite is an antiferromagnetic material below the Morin transition at 250 K (−23 °C; −10 °F), and a canted antiferromagnet or weakly ferromagnetic above the Morin transition and below its Néel temperature 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 magnetic moment (0.002 µB). 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 which causes the moments to align along the c axis. In this configuration, spin canting does not reduce the energy. [9] [10] The magnetic properties of bulk hematite differ from their nanoscale counterparts. For example, the Morin transition temperature of hematite decreases with a decrease in the particle size. The suppression of this transition has also been observed in some of the hematite nanoparticles, and the presence of impurities, water molecules and defects in the crystals were attributed to the absence of a Morin transition. Hematite is part of a complex solid solution oxyhydroxide system having various contents of water, hydroxyl groups and vacancy substitutions that affect the mineral's magnetic and crystal chemical properties. [11] Two other end-members are referred to as protohematite and hydrohematite.

Enhanced magnetic coercivities for hematite have been achieved by dry-heating a 2-line ferrihydrite precursor prepared from solution. Hematite exhibited temperature-dependent magnetic coercivity values ranging from 289 to 5,027 Oe. The origin of these high coercivity values has been interpreted as a consequence of the subparticle structure induced by the different particle and crystallite size growth rates at increasing annealing temperature. These differences in the growth rates are translated into a progressive development of a subparticle structure at the nanoscale. At lower temperatures (350–600 °C), single particles crystallize however; at higher temperatures (600–1000 °C), the growth of crystalline aggregates with a subparticle structure is favored. [12]

Mine tailings

Hematite is present in the waste tailings of iron mines. A recently developed process, magnetation, uses magnets to glean waste hematite from old mine tailings in Minnesota's vast Mesabi Range iron district. [13] Falu red is a pigment used in traditional Swedish house paints. Originally, it was made from tailings of the Falu mine. [14]

Mars

Image mosaic from the Mars Exploration Rover Microscopic Imager shows Hematite spherules partly embedded in rock at the Opportunity landing site. Image is ca. 5 cm (2 in) across. 07-ml-3-soil-mosaic-B019R1 br.jpg
Image mosaic from the Mars Exploration Rover Microscopic Imager shows Hematite spherules partly embedded in rock at the Opportunity landing site. Image is ca. 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. [15] The mineral was seen in abundance at two sites [16] on the planet, the Terra Meridiani site, near the Martian equator at 0° longitude, and the Aram Chaos site near the Valles Marineris. [17] Several other sites also showed hematite, e.g., Aureum Chaos. [18] 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 sent to a site in the Terra Meridiani region designated Meridiani Planum. 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 named "blueberries" by the science team. Analysis indicates that these spherules are apparently concretions 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". [19]

Jewellery

Hematite's popularity in jewellery rose in England during the Victorian era, due to its use in mourning jewellery. [20] [21] Certain types of hematite or iron oxide-rich clay, especially Armenian bole, have been used in gilding. Hematite is also used in art such as in the creation of intaglio engraved gems. Hematine is a synthetic material sold as magnetic hematite. [22]

See also

Related Research Articles

Ferromagnetism physical phenomenon

Ferromagnetism is the basic mechanism by which certain materials form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished. Ferromagnetism is the strongest type and is responsible for the common phenomena of magnetism in magnets encountered in everyday life. Substances respond weakly to magnetic fields with three other types of magnetism—paramagnetism, diamagnetism, and antiferromagnetism—but the forces are usually so weak that they can only be detected by sensitive instruments in a laboratory. An everyday example of ferromagnetism is a refrigerator magnet used to hold notes on a refrigerator door. The attraction between a magnet and ferromagnetic material is "the quality of magnetism first apparent to the ancient world, and to us today".

Limonite Oxide mineral

Limonite is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the three principal iron ores, the others being hematite and magnetite, and has been mined for the production of iron since at least 2500 BCE.

Antiferromagnetism magnetic ordering

In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins pointing in opposite directions. This is, like ferromagnetism and ferrimagnetism, a manifestation of ordered magnetism.

Ferrimagnetism Type of magnetic phenomenon

In physics, a ferrimagnetic material is one that has populations of atoms with opposing magnetic moments, as in antiferromagnetism; however, in ferrimagnetic materials, the opposing moments are unequal and a spontaneous magnetization remains. This happens when the populations consist of different materials or ions (such as Fe2+ and Fe3+).

Neodymium magnet type of magnet

A neodymium magnet (also known as NdFeB, NIB or Neo magnet), the most widely used type of rare-earth magnet, is a permanent magnet made from an alloy of neodymium, iron and boron to form the Nd2Fe14B tetragonal crystalline structure. Developed independently in 1982 by General Motors and Sumitomo Special Metals, neodymium magnets are the strongest type of permanent magnet commercially available. Due to different manufacturing processes, they are also divided into two subcategories, namely sintered NdFeB magnets and bonded NdFeB magnets. They have replaced other types of magnets in many applications in modern products that require strong permanent magnets, such as motors in cordless tools, hard disk drives and magnetic fasteners.

Meridiani Planum plain located 2 degrees south of Mars equator

Meridiani Planum is a plain located 2 degrees south of Mars's equator, in the westernmost portion of Terra Meridiani. It hosts a rare occurrence of gray crystalline hematite. On Earth, hematite is often formed in hot springs or in standing pools of water; therefore, many scientists believe that the hematite at Meridiani Planum may be indicative of ancient hot springs or that the environment contained liquid water. The hematite is part of a layered sedimentary rock formation about 200 to 800 meters thick. Other features of Meridiani Planum include volcanic basalt and impact craters.

Sinus Meridiani albedo feature on Mars

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Rock magnetism The study of magnetism in rocks

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Iron(II,III) oxide chemical compound

Iron(II,III) oxide is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe2O3) also known as hematite. It contains both Fe2+ and Fe3+ ions and is sometimes formulated as FeO ∙ Fe2O3. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic, but is sometimes incorrectly described as ferromagnetic. Its most extensive use is as a black pigment. For this purpose, it is synthesised rather than being extracted from the naturally occurring mineral as the particle size and shape can be varied by the method of production.

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Aram Chaos chaos on Mars

Aram Chaos, centered at 2.6°N, 21.5°W, is 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. Aram Chaos takes its name from Aram, one of the classical albedo features observed by Giovanni Schiaparelli, who named it after the Biblical land of Aram. Spectroscopic observation from orbit indicates the presence of the mineral hematite, likely a signature of a once aqueous environment.

The Morin transition (also known as a spin-flop 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.

Mars surface color

The surface of the planet Mars appears reddish from a distance because of rusty dust suspended in the atmosphere. From closeup, it looks more of a butterscotch, and other common surface colors include golden, brown, tan, and greenish, depending on minerals.

An orthoferrite is any of a class of chemical compounds with the formula RFeO3, where R is one or more rare-earth elements. Orthoferrites have an orthorhombic crystal structure with a space group Pbnm and most are weakly ferromagnetic. At the Néel temperature TN the subsystem of iron ions orders into a slightly canted antiferromagnetic structure with antiferromagnetic moment G and a weak ferromagnetic moment F. The rare-earth ion subsystem acquires magnetization m due to an interaction with the iron subsystem. The orthoferrites are particularly interesting because of the presence of an antisymmetric exchange interaction which involves the vector cross product of neighboring spins as opposed to the usual scalar product. In the absence of this interaction, the orthoferrites would be antiferromagnetic. Its presence leads to a small canting of the sublattices, making the orthoferrites “weak” ferromagnets with 4πMs = 100 G. Another interesting feature of these materials is the fact that some of them exhibit a transition as a function of temperature, in which the direction of the antiferromagnetically ordered spins and consequently also of the net magnetization rotates by 90°.

Iron oxide nanoparticles are iron oxide particles with diameters between about 1 and 100 nanometers. The two main forms are magnetite (Fe3O4) and its oxidized form maghemite (γ-Fe2O3). They have attracted extensive interest due to their superparamagnetic properties and their potential applications in many fields (although Co and Ni are also highly magnetic materials, they are toxic and easily oxidized).

Magnetic mineralogy is the study of the magnetic properties of minerals. The contribution of a mineral to the total magnetism of a rock depends strongly on the type of magnetic order or disorder. Magnetically disordered minerals contribute a weak magnetism and have no remanence. The more important minerals for rock magnetism are the minerals that can be magnetically ordered, at least at some temperatures. These are the ferromagnets, ferrimagnets and certain kinds of antiferromagnets. These minerals have a much stronger response to the field and can have a remanence.

Composition of Mars Branch of the Geology of Mars

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References

  1. Dunlop, David J.; Özdemir, Özden (2001). Rock Magnetism: Fundamentals and Frontiers. Cambridge: Cambridge University Press. p. 73. ISBN   9780521000987.
  2. Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (eds.). "Hematite" (PDF). Handbook of Mineralogy. III (Halides, Hydroxides, Oxides). Chantilly, VA, US: Mineralogical Society of America. ISBN   978-0962209727 . Retrieved December 22, 2018.
  3. "Hematite Mineral Data". WebMineral.com. Retrieved December 22, 2018.
  4. "Hematite". Mindat.org. Retrieved December 22, 2018.
  5. 1 2 Cornell, Rochelle M.; Schwertmann, Udo (1996). The Iron Oxides. Germany: Wiley. pp. 4, 26. ISBN   9783527285761. LCCN   96031931 . Retrieved December 22, 2018.
  6. 1 2 "Ochre". Industrial Minerals. Minerals Zone. Archived from the original on November 15, 2016. Retrieved December 22, 2018.
  7. "Researchers find earliest evidence for modern human behavior in South Africa" (Press release). AAAS. ASU News. October 17, 2007. Retrieved December 22, 2018.
  8. Levato, Chiara (2016). "Iron Oxides Prehistoric Mines: A European Overview" (PDF). Anthropologica et Præhistorica. 126: 9–23. Retrieved December 22, 2018.
  9. Dzyaloshinsky, I.E. (1958). "A thermodynamic theory of "weak" ferromagnetism of antiferromagnetics". Journal of Physics and Chemistry of Solids. 4 (4): 241–255. Bibcode:1958JPCS....4..241D. doi:10.1016/0022-3697(58)90076-3.
  10. Moriya, Tôru (1960). "Anisotropic Superexchange Interaction and Weak Ferromagnetism". Physical Reviews Journal. 120 (1): 91. Bibcode:1960PhRv..120...91M. doi:10.1103/PhysRev.120.91.
  11. Dang, M.-Z.; Rancourt, D.G.; Dutrizac, J.E.; Lamarche, G.; Provencher, R. (1998). "Interplay of surface conditions, particle size, stoichiometry, cell parameters, and magnetism in synthetic hematite-like materials". Hyperfine Interactions. 117 (1–4): 271–319. Bibcode:1998HyInt.117..271D. doi:10.1023/A:1012655729417.
  12. Vallina, B.; Rodriguez-Blanco, J.D.; Brown, A.P.; Benning, L.G.; Blanco, J.A. (2014). "Enhanced magnetic coercivity of α-Fe2O3 obtained from carbonated 2-line ferrihydrite". Journal of Nanoparticle Research. 16 (3): 2322. Bibcode:2014JNR....16.2322V. doi:10.1007/s11051-014-2322-5.
  13. Redman, Chris (May 20, 2009). "The next iron rush". Money.cnn.com. Retrieved December 22, 2018.
  14. "Sveriges mest beprövade husfärg" [Sweden's most proven house color] (in Northern Sami). Retrieved December 22, 2018.
  15. "Mars Global Surveyor TES Instrument Identification of Hematite on Mars" (Press release). NASA. May 27, 1998. Archived from the original on May 13, 2007. Retrieved December 22, 2018.
  16. Bandfield, Joshua L. (2002). "Global mineral distributions on Mars" (PDF). Journal of Geophysical Research. 107 (E6): E65042. Bibcode:2002JGRE..107.5042B. doi:10.1029/2001JE001510.
  17. Glotch, Timothy D.; Christensen, Philip R. (2005). "Geologic and mineralogic mapping of Aram Chaos: Evidence for a water-rich history". Journal of Geophysical Research. 110 (E9): E09006. Bibcode:2005JGRE..110.9006G. doi:10.1029/2004JE002389.
  18. Glotch, Timothy D.; Rogers, D.; Christensen, Philip R. (2005). "A Newly Discovered Hematite-Rich Unit in Aureum Chaos: Comparison of Hematite and Associated Units With Those in Aram Chaos" (PDF). Lunar and Planetary Science XXXVI: 2159. Bibcode:2005LPI....36.2159G.
  19. "Hematite". NASA. Retrieved December 22, 2018.
  20. "Black Gemstones, Diamonds and Opals: The Popular New Jewelry Trend". TrueFacet.com. October 23, 2015. Retrieved December 22, 2018.
  21. "(What's the Story) Mourning Jewelry?" . Retrieved December 22, 2018.
  22. "Magnetic Hematite". Mindat.org. Retrieved December 22, 2018.