![]() Mixing is followed by injection of air into the cell. In the cell the ore is mixed with water and “floatation agents”. Froth floatation is a method of beneficiation which relies on the differences between the surface chemistry of the country rock and the mineral being extracted, in this case graphite flake. The graphite/ore-rock slurry is then fed to froth floatation cells. At this point the individual flakes have been freed from the enclosing ore rock. Reduced ore is then feed to a mill where the ore is crushed further. Crushing must be done in order to release the flake from the enclosing country rock. Processing of hard rock ore starts by trucking the ore to a crusher. The ore can be either quarried, open pit style, or shaft mined depending on the proximity of the ore body to the surface. Highly weathered ore can literally be dug and hauled like sand to the floatation plant. If the ore is hard-rock, it must be drilled and blasted. Most commercially significant deposits for flake graphite are probably of organic origin (Please refer to the section on Organic Petrology, located else where in these pages for more information on organically derived graphite).ĭepending on the degree of weathering of the ore rock, flake graphite is mined using standard hard or soft rock mining techniques. Inorganic carbon is carbon that was derived from previously formed carbonate minerals or some other non-biological source of carbon such as carbonatites which are igneous derived carbonate rocks. Algae, in the form of algal mats are considered possible source material for pre-graphitic carbon. An example would be some ancient benthic micro-organism that died and fell to the sea bottom along with countless billions of others such organisms forming a lens or layer of carbonaceous sediment. What is meant by “organic carbon” is that the source material is biological in nature. Graphite must have a reducing environment in order to be stable at high temperature.įlake graphite can begin its geological life as either an organic or inorganic carbon. Since graphite is a form of carbon, and all carbon oxidizes at high temperature, a geologic environment in which nascent or otherwise reactive oxygen is present will preclude the formation of graphite. Graphite flake may form under pressures of 75,000 psi (1GPa) and 1380 deg. This is a high pressure and high temperature environment. Metamorphic petrologists classify the environment in which flake graphite formed as “Granulite facies” (see section on Metamorphism elsewhere in these pages). A typical rock type where flake graphite may be found is sulphidic biotite-quarz-feldspar gneiss such is the rock type of the Mesoproterozoic graphite deposits in the “Highlands” region of New Jersey, USA (Volkert, Johnson, Tamashausky, 2000).įlake graphite is considered a “high-grade” metamorphic mineral. Most economic deposits of flake graphite occur in metamorphic rock. Small, localized deposits of flake or flake-like graphite are known from literally hundreds of other localities.Īs with other types of natural graphite, flake graphite is formed in either metamorphic or igneous geologic environments. Large deposits of flake graphite have been mined in the United States of America, Central America, South America, Canada, Africa, Germany, Ukraine, Russia, and China. The two polarized light images are of a growth spiral on the pinacoid surface of a flake (Light microscopy images courtesy of John Jaszczak, MTU).įlake graphite is the most geologically common variety of natural graphite. The prominent form (crystal face) visible in these micrographs is the basal pinacoid, form is clearly visible in the photograph of the graphite flake imbedded in calcite. ![]() The black and white images are scanning electron micrographs. ![]() The platy morphology of flake graphite is illustrated in the scanning electron and polarized light micrographs presented below: All graphite has a flaky morphology on some level, but in most instances flake-graphite has this structure regardless of particle size. As the name implies flake graphite has a distinctly flaky or platy morphology. ![]() Both of these products typically contain flake graphite. Most people are familiar with the finely powdered graphite used as a lock lubricant, or the “lead” in pencils. Flake-graphite is probably the most familiar of the natural graphite materials.
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