Hematite other names

Structural relationships exist between certain planes in the hematite structure and those in other iron oxides, namely magnetite and goethite (Tab. 2.6). There is, for example, a relationship between the (111) plane of magnetite and (001) plane of hema-... 

Iron (III) oxide exists in mineral form as hematite. It is 70% iron and is the primary source of iron ore in the world. About 90% of the iron mined in the United States is hematite. World production of this ore is more than 1 billion tons. Magnetite and taconite are two other primary iron oxide minerals used as iron ore. The name hematite comes from the blood-red color of powdered hematite. The Greek word hematite means blood-like. Some ancients held the belief that hematite was formed in areas where batdes were fought and blood was spilled into the earth. Large deposits of hematite have been identified on Mars. 

Sedimentary rocks with the highest arsenic concentrations largely consist of materials that readily sorb or contain arsenic, such as organic matter, iron (oxy)(hydr)oxides, clay minerals, and sulfide compounds. Arsenian pyrite and arsenic-sorbing organic matter are especially common in coals and shales. Ironstones and iron formations are mainly composed of hematite and other iron (oxy)(hydr)oxides that readily sorb or coprecipitate arsenic. Iron compounds also occur as cements in some sandstones. Although almost any type of sedimentary rock could contain arsenic-rich minerals precipitated by subsurface fluids (Section 3.6.4), many sandstones and carbonates consist almost entirely of minerals that by themselves retain very little arsenic namely, quartz in sandstones and dolomite and calcite in limestones. 

A few frequently cited values of PZCs/IEPs have actually never been published. Namely, they have been cited after secondary sources, without checking the primary source, which reports different PZCs/IEPs than that in a secondary source, a result of limited significance, or no PZCs/IEPs at all. Reference [2469] is quoted in [1] and then by a few other authors (probably after [1]) as an authoritative source of the IEP of hematite. Actually, no specific IEP is reported in [2469]. The authors mention that pH 2.4-4.2 is far from the IEP, but they do not specify how far. 

Absorption. The other factor that is particular to different materials is the optical absorption. The absorption spectrum can easily distinguish different gems. Although laboratory instruments are best, gemologists can use a hand-held spectrometer. Hematite is gray unless the light passes through it, in which case it appears red (hence its name). A streak of hematite will appear red for the same reason hematite with powder on the surface appears red. The reason for the red color is that hematite absorbs blue... 

The other structures of interest are those ivith the basic formula M2O3, O/M = 1.5. There are tv o of these structures found in CICPs, one being corundum, named after the a-alumina phase of AI2O3, and the other is hematite named after the mineral Fe203. There is a slight difference in spatial geometry betiveen the tv o structures, but both are quite similar. Metal ions are trivalent and octahedrally coordinated in both. 

More recent applications of the term (Bikiaris et ai, 1999 Daniila et al., 2002 Oliveira et al., 2002) appear to refer to naturally occurring and heat treated hematite-rich pigments producing a violet colour used in Roman, Byzantine and post-Byzantine art. Here, and perhaps due to the Latin name, caput mortuum is directly related to the purple pigments documented by the Roman authors Pliny (77 AD) and Vitruvius (first century BC), although the name was never used by either and in fact is unknown from other classical sources. However, it has been used synonymously with Pliny s and Vitruvius usta and ostrum although the link between these materials is, al best, tenuous. The pigments of these names described by Vitruvius refer specifically to T)rian purple and Pliny s usta refers to burnt cerussa (red lead qq.v.). 

Some more recent attempts were made to construct deformation mechanism maps for the three oxides, namely wustite, magnetite and hematite [118-120]. Deformation mechanism maps were introduced by Ashby and Frost [121] as a tool to identify the predominant deformation mechanisms and the rates of deformation (strain rates) imder certain stress and temperature conditions for solid metals and ceramics. However, the maps constructed for iron oxides were primarily based on theoretical calculation because experimental data available were very limited and estimation was based on data from other oxide systems. 

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