“…The growth of CNTs on natural materials is a potential way to achieve environmentally benign and low-cost production. [258] A variety of minerals (such as volcanic lava rock, bentonite, soil, [258] garnet sand, [259] wollastonites, [260] montmorillonite, [261] sepiolite, [262] and vermiculite, [113,210,212] ), biomass-derived materials (such as activated carbon, [263] black jew's-ear fungus and black sesame seeds [264] ), and industrial wastes (such as red mud [265] and fly ash [266] ), have been used as catalysts and/or catalyst supports for the synthesis of CNTs. Organic natural materials, such as coal, [267] natural gas, [268] liquefied petroleum gas, [269] eucalyptus oil, [270] turpentine oil, [271] camphor, [272] deoiled asphalt, [273] even grass, [274] can serve as the carbon source for CNT synthesis.…”