Vein graphite

One useful classification of graphite depends on the mode of formation that leads to three physically distinct common varieties dake, lump, and amorphous. The term dake is self-explanatory dake forms occur disseminated in rock. Lump graphite occurs in fissure-filled veins in pegmatite dikes, also associated with chip and the rarer needle forms. Amorphous graphite occurs in beds that were once coal, but fine-grained, easily ground vein graphite is also classified as amorphous. 

Flake graphite, amorphous graphite, vein graphite, synthetic graphite, intumescent flake graphite (expandable graphite)... 

Purified crystaDine fiake and crystalline vein graphite carbon (LOI) 99.7-99.9%... 

Flake graphite is found disseminated in metamorphosed silica-rich quartzites, gneisses, and marbles. Crystalline (vein) graphite occurs in transverse, igneous, or metamorphic rocks, where it was formed by the transformation of oil precursors. Amorphous graphite is the result of the metamorphosis of coal exposed to high pressure. Graphite is also present in the universe as evidenced by near-perfect crystals frequently found in meteorites. 

Several lines of gr hite products amorphous graphite, crystaUine flake graphite, crystalline vein graphite, Desulcu, synthetic graphite, ThermoPure. The particle sizes of these graphites are from pm to mm. 

AH graphite has crystal stmcture but only certain kinds and sizes of natural graphites are commercially classified as crystalline, a term used for import duty purposes. Throughout this article reference is made separately to dake, vein (lump or high crystalline), and amorphous forms, all of which are essentially the same crystalline form of carbon. However, fine stmctured graphites (cryptocrystalline (2)) have been classified as amorphous. 

In the same vein, fig. 2.28 Illustrates the adsorption of long chain n-alkanes from n-heptane on different grades of graphite, to compare their surface properties. One of these adsorbents, Vulcan 3G, was a standard sample especially prepared under lUPAC auspices. The enthalpies were measured as displacement enthalpies in a flow calorimeter. All enthalpy and adsorption isotherms are S-shaped. In fig. 2.28a, right, is plotted as a function of for the... 

Schopf et al. (2002) and earlier work cited therein, found evidence for microbial fossils in Pilbara and Barberton material. The laser-Raman imagery reported by Schopf et al. (2002) demonstrated that the material was made of kerogen and they interpreted this as evidence for remains microbial life. Brasier et al. disputed the earlier work by Schopf and Packer (1987) and Schopf (1993) on Warrawoona material, constmcting a detailed case in which they reinterpreted the supposed microfossils of the earlier study as secondary artifacts of graphite in hydrothermal veins. However, Brasier et al. (2002) did report C isotopic results that are most easily (though not conclusively) interpreted as microbial. Thus although... 

Since the chosen pressure of 1 bar represents the selected standard state, we designate the standard molar enthalpy of pure i at temperature T by the symbol = 0. However, the asterisk is ordinarily omitted, it being understood that element i is in its pure state. One must be careful in the application of this rule for example, the stable configuration of carbon at room temperature and ambient pressure is graphite, not diamond. In the same vein, sulfur under these conditions is stable in the rhombic habit, and Sn, in the white rather than the grey crystalline state. As another example, Br2 at P = 1 bar and 300 K is a liquid, while as a participant in reactions at 500 K Br2 is in the gaseous state. 

At Totsugawa, south of Kioto, the vein cuts through a quartzitio and graphitic schist. (A.)... 

With respect to graphite, the following bulk price ranges per ton have been reported depending upon type, grade (particle size), purity, and quantity ordered Flake, 650-2250 amorphous, 550-1000 vein, 2000—4000 synthetic, 650-2500 expandable, 2000-4000. 

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