red sandstone iron oide electomagetic properties

ochre - the oldest known natural pigment in the world

Ochre (rarely spelled ocher and often referred to as yellow ochre) is one of a variety of forms of iron oxide which are described as earth-based pigments. These pigments, used by ancient and modern artists, are made of iron oxyhydroxide, which is to say they are natural minerals and compounds composed of varying proportions of iron (Fe3 or Fe2), oxygen (O) and hydrogen (H).

Other natural forms of earth pigments related to ochre include sienna, which is similar to yellow ochre but warmer in color and more translucent; and umber, which has goethite as its primary component and incorporates various levels of manganese. Red oxides or red ochres are hematite-rich forms of yellow ochres, commonly formed from aerobic natural weathering of iron-bearing minerals.

Natural iron-rich oxides provided red-yellow-brown paints and dyes for a wide range of prehistoric uses, including but in no way limited to rock art paintings, pottery, wall paintings and cave art, and human tattoos. Ochre is the earliest known pigment used by humans to paint our world--perhaps as long ago as 300,000 years. Other documented or implied uses are as medicines, as a preservative agent for animal hide preparation, and as a loading agent for adhesives (calledmastics).

Ochre is often associated with human burials: for example, the Upper Paleolithic cave site of Arene Candide has an early use of ochre at a burial of a young man 23,500 years ago. The site of Paviland Cave in the UK, dated to about the same time, had a burial so soaked in red ochre he was (somewhat mistakenly) called the "Red Lady".

Before the 18th and 19th century, most pigments used by artists were of natural origin, made up of mixtures of organic dyes, resins, waxes, and minerals. Natural earth pigments like ochres consist of three parts: the principle color-producing component (hydrous or anhydrous iron oxide), the secondary or modifying color component (manganese oxides within umbers or carbonaceous material within brown or black pigments) and the base or carrier of the color (almost always clay, the weathered product of silicate rocks).

Ochre is thought generally to be red, but in fact is a naturally-occurring yellow mineral pigment, consisting of clay, siliceous materials and the hydrated form of iron oxide known as limonite. Limonite is a general term referring to all forms of hydrated iron oxide, including goethite, which is the fundamental component of the ochre earths.

Ochre contains a minimum of 12% iron oxyhydroxide, but the amount can range up to 30% or more, giving rise to the wide range of colors from light yellow to red and brown. The intensity of color depends on the degree of oxidation and hydration of the iron oxides, and the color becomes browner depending on the percentage of manganese dioxide, and redder based on the percentage of hematite.

Since ochre is sensitive to oxidation and hydration, the yellow can be turned red by heating goethite (FeOOH) bearing pigments in yellow earth and converting some of it to hematite. Exposing yellow goethite to temperatures above 300 degrees Celcius will gradually dehydrate the mineral, converting it first to orange-yellow and then red as hematite is produced. Evidence of heat-treatment of ochre dates at least as early as the Middle Stone Age deposits in Blombos cave, South Africa.

Ochre is very common on archaeological sites worldwide. Certainly, Upper Paleolithic cave art in Europe and Australia contain the generous use of the mineral: but ochre use is much older. The earliest possible use of ochre discovered so far is from a Homo erectus site about 285,000 years old. At the site called GnJh-03 in the Kapthurin formation of Kenya, a total of five kilograms (11 pounds) of ochre in more than 70 pieces was discovered.

Ochre was part of the first art of the Middle Stone Age (MSA) phase in Africa called Howiesons Poort. The early modern human assemblages of 100,000-year-old MSA sites including Blombos Cave and Klein Kliphuis in South Africa have been found to include examples of engraved ochre, slabs of ochre with carved patterns deliberately cut into the surface.

Spanish paleontologist Carlos Duarte (2014) has even suggested that using red ochre as a pigment in tattoos (and otherwise ingested) may have had a role in human evolution, as it would have been a source of iron directly to the human brain, perhaps making us smarter. The presence of ochre mixed with milk proteins on an artifact from a 49,000-year-old MSA level at Sibudu cave in South Africa is suggested to have been used to make the ochre liquid, probably by killing a lactating bovid (Villa 2015).

The yellow-red-brown ochre pigments used in paintings and dyes are often a mixture of mineral elements, both in their natural state and as a result of deliberate mixing by the artist. Much of recent research on ochre and its natural earth relatives has been focused on identifying the specific elements of a pigment used in a particular paint or dye. Determining what a pigment is made up of allows the archaeologist to find out the source where the paint was mined or collected, which could provide information about long-distance trade. Mineral analysis helps in conservation and restoration practices; and in modern art studies, assists in the technical examination for authentication, identification of a specific artist, or the objective description of an artist's techniques.

Such analyses have been difficult in the past because older techniques required the destruction of some of the paint fragments. More recently, studies that use microscopic amounts of paint or even completely non-invasive studies such as various types of spectrometry, digital microscopy, x-ray fluorescence, spectral reflectance, and x-ray diffraction have been used successfully to split out the minerals used, and determine the type and treatment of the pigment.

electromagnetic shielding properties of iron oxide impregnated kenaf bast fiberboard - sciencedirect

The electromagnetic shielding effectiveness of kenaf fiber based composites with different iron oxide impregnation levels was investigated. The kenaf fibers were retted for removing the lignin and extractives from the fibers and magnetized. Using the unsaturated polyester and the magnetized fibers, kenaf fiber based composites were manufactured by the compression molding process. The transmission energies of the composites were characterized when the composite samples were exposed under the irradiation of electromagnetic (EM) wave with a variable frequency from 9GHz to 11GHz. Using the Scanning Electron Microscope (SEM), the iron oxide nanoparticles were observed on the surfaces and inside the micropore structures of single fibers. As the Fe content increased from 0% to 6.8%, 15.9% and 18.0%, the total surface free energy of kenaf fibers with the magnetizing treatments increased from 44.8mJ/m2 to 46.1mJ/m2, 48.8mJ/m2 and 53.0mJ/m2, respectively, while the modulus of elasticity reduced from 2875MPa to 2729MPa, 2487MPa and 2007MPa, respectively. Meanwhile, the shielding effectiveness was increased from 3050% to 6070%, 6575% and 7080%, respectively.

understanding genesis of iron oxide concretions present in dhandraul (vindhyan) sandstone: implications in formation of martian hematite spherules | springerlink

The iron oxide concretions of Shankargarh (Allahabad), India belongs to Dhandraul Sandstone of Vindhyan Supergroup. Petrography of concretions shows abundant quartz grains embedded within the iron oxide cementation. XRD analysis of the concretion shows diagnostic peaks for quartz, hematite, and goethite. The ACNK and ACNKFM ternary diagrams drawn for concretion and host rock bulk composition clearly indicate the interaction of concretions rock with iron-bearing diagenetic fluids. A negative Ce anomaly, lower Th/U ratio, and enrichment of redox responsive trace element (e.g., vanadium) indicate concretion formation is redox-controlled. The concretions show Fe enrichment and Si depletion as compared to the host sandstone. The mass balance calculations indicate that the total Fe2O3 in the ferruginous sandstone system is 17.63 wt%. The iron mobilization and recycling in the sandstone pore spaces have formed concretions with Fe2O3 (2535% by volume). The sandstone volume required to produce a 6 mm diameter iron oxide concretion is 1807.83 mm3. The Fe laminae and random red colouration patterns in Dhandraul sandstone are consistent with the movement of iron-enriched fluid through pores and spaces. These iron oxide concretions have similarities with the hematite spherules discovered in the Burn Formation, Meridiani Planum, Mars.

Fe bearing paleofluid circulation, redox processes, and elemental mobility (enrichment and depletion of elements) are discussed in detail using whole-rock geochemistry of Shankargarh iron oxide concretions and associated sandstone.

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Mr Prakash Jha acknowledges IIT (ISM) Dhanbad for the Institute fellowship. The authors acknowledge the XRF analysis facility at NGRI Hyderabad (India), ICPMS analysis facility at IIT Kanpur (India), and XRD analysis facility at SRM University, Chennai, India.

Mr Prakash Jha has done the fieldwork, petrography, and analyzed the photographs and data generated from it. He has also analyzed the geochemical data generated from various scientific labs and organizations. Mr Prakash Jha, Dr Pranab Das and Dr Dwijesh Ray have cooperatively written this research paper.

Jha, P., Das, P. & Ray, D. Understanding genesis of iron oxide concretions present in Dhandraul (Vindhyan) Sandstone: Implications in formation of Martian hematite spherules. J Earth Syst Sci 130, 49 (2021). https://doi.org/10.1007/s12040-020-01542-6

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iron oxide (fe2o3) - structure, molecular mass, properties & uses

It occurs in nature very abundantly and widely distributed. It is a chemical complexes which occur naturally comprising iron and oxygen. Iron oxide are vital to humans and useful in most geological and biological activities. This iron oxide may be required for investigations of their own particular properties or used as starting materials for other processes.

Frequently Asked QuestionsIs iron oxide toxic to humans? Iron oxide when breathed in will impact you. Exposure to fumes from Iron Oxide can cause fever from metal fumes. This is a flu-like condition with metallic taste signs, fever and chills, aches, chest tightness and cough. Ferrous Oxide (FeO), however, is highly flammable and reactive, and can spontaneously combust in air. What is Fe3O4 called? FeO is called ferrous oxide while Fe2O3 is ferric oxide. So the Fe3O4 compound is called ferrous ferric oxide. What is the difference between Fe2O3 and Fe3O4? They are ferrous oxides. Thus, Fe2O3 is a simple oxide where Fe is only + 3 in the oxidation state thus Fe3O4 is a mixed oxide where Fe is present in both + 2 and + 3 oxidation states. However, we compose Fe3O4 as FeO. Fe2O3 is written as iron oxide (III) while Fe3O4 is written as iron oxide (II, III). What is iron oxide made of? Iron oxides are compounds that are composed of iron and oxygen. There are seventeen known iron oxides and oxyhydroxides, of which the best known is rust, a type of iron oxide(III). Iron oxides and oxyhydroxides are common in nature and play a significant role in many processes, both geological and biological. What is black iron oxide used for? Black iron oxide or magnetite is used for resistance to corrosion, too. Often used in anti-corrosion paints is black iron oxide (found in many bridges, and Eiffel Tower). Iron oxides are used to shorten proton relaxation times (T1, T2 and T2) as a contrast agent in magnetic resonance imaging.

Iron oxide when breathed in will impact you. Exposure to fumes from Iron Oxide can cause fever from metal fumes. This is a flu-like condition with metallic taste signs, fever and chills, aches, chest tightness and cough. Ferrous Oxide (FeO), however, is highly flammable and reactive, and can spontaneously combust in air.

They are ferrous oxides. Thus, Fe2O3 is a simple oxide where Fe is only + 3 in the oxidation state thus Fe3O4 is a mixed oxide where Fe is present in both + 2 and + 3 oxidation states. However, we compose Fe3O4 as FeO. Fe2O3 is written as iron oxide (III) while Fe3O4 is written as iron oxide (II, III).

Iron oxides are compounds that are composed of iron and oxygen. There are seventeen known iron oxides and oxyhydroxides, of which the best known is rust, a type of iron oxide(III). Iron oxides and oxyhydroxides are common in nature and play a significant role in many processes, both geological and biological.

Black iron oxide or magnetite is used for resistance to corrosion, too. Often used in anti-corrosion paints is black iron oxide (found in many bridges, and Eiffel Tower). Iron oxides are used to shorten proton relaxation times (T1, T2 and T2) as a contrast agent in magnetic resonance imaging.

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