Magnetite color

Copper salts usually are the result of corrosion in the post-boiler section and may be present as red cuprous oxide (Cu20), black cupric oxide (CuO), or blue-green copper sulfate (CuSO ). Mostly, copper salts are mixed with hematite and magnetite and take on a black color. 

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. 

The mechanism of the scaling of iron is so complex as to require special mention. Above 570 °C, wiistite (Fei xO) is thermodynamically stable and forms the relatively thick basal layer in the oxide film. This is followed by a magnetite (FesCU) layer which is followed by a final layer of Fe2C>3. Magnetite itself tends to become nonstoichiometric under oxidizing conditions, with excess Fe3+, so that its composition and color can vary from Fe3.oooC>4 (black) toward cubic Fe2.667 04 (i.e., 7-Fe203, chocolate brown). Thus, as outlined in Section 4.6, the oxidation of iron above 570 °C involves mainly... 

Fe304, magnetite [1309-38-2], spinel structure, ferrimagnetic, color black... 

Emery is a mixture of granular corundum of dark color, magnetite and hematite, sometimes with spinel. Quartz may be present For a long time emery was supposed to be an ore of iron. Until the introduction of artificial abrasives, emery was much used for such purposes. 

A form of rust. Magnetic gray-to-red colored iron oxide (Fe2C>3) offering no protection from further corrosion usually the first signs of steel corrosion and often followed by formation of magnetite. 

Fig. 10 (a, b) Schematic mechanism demonstrated for a reflective color M-paper with magnetically controllable characteristics, (c, d) The intensity of magnetic field dependence on the reflection spectra of chiral nematic mixtures doped with magnetite nanoparticles that are surface modified with oleic acid and a chiral pyridine-based dopant, as well as photographs of both formulations before and after a magnetic field of 1,000 GS was applied (see photograph insets above) [364], (Copyright 2010, Taylor Francis)... 

Figure 1.2. Light micrograph of the radula of the chiton Acanthopleura haddoni, showing 46 tooth rows. On the right hand side of the figure the first seven tooth rows are totally transparent (not mineralized), while in the next four rows the first mineral deposits appear. The dark color is due to the iron oxide mineral, magnetite.

The first row of teeth with extracellular mineral in the framework has an ochre color. This is due to large accumulations of ferrihydrite granules. The iron is derived from the ferritin in the epithelial cells, but is transported out of the cells in the soluble reduced form [14]. Within a row or two the color darkens as the ferrihydrite precursor mineral converts to magnetite. All of the above is confined to the posterior tooth layer that is ultimately composed entirely of magnetite (Fe0.Fe203) [11,13]. 

Fe304 magnetite C.I. Pigment Black 11 1317-61-9 1309-38-2 12227-89-3 spinel ferrimagnetic color black... 

Figure 32.38. Magnetotactic Bacterium. The magnetosome, visible as a chain of opaque membrane-bound magnetite crystals, acts as a compass to orient the bacteria with the earth s magnetic field. The bacterium is artificially colored. [Courtesy of Richard B. Frankel, California Polytechnic State University, San Luis Obispo, California.]...

Figure 6 Magnetite. The crystal structure of magnetite, a member of the spinel group of minerals. The [111] crystallographic direction is vertical to show the horizontal appearance of cubic-close-packed oxygen (O) atoms. Fe and Fe are in tetrahedral and in octahedral interstices (both dark colored) (after Gaines et al., 1997, p. 293).

Once the syntheses are underway, the lecture can be presented. The graphs for this section as well as the list of oxides in the introduction should be available for presentation as slides or overheads. It is worth using colors for the different Fe oxides and these should be mnemonic and of course, the same on all graphs, namely, black for magnetite, red for hematite, brown for ferrihydrite, yellow for goethite and orange for lepidocrocite (Schwertmann, 1993). 

Golden, D. C. D., Ming, W., Bowen, L. H., Morris, R. V and Lauer, Jr. H. V (1994) Acidified oxalate and dithionite solubUity and color of synthetic, partially oxidized Al-magnetites and their thermal oxidation products. Clays Clay Min. 42 53-62. 

---