Synthesis of carbon nanotubes (CNTs) via chemical vapor deposition (CVD) has been intensively investigated for it is among the most promising techniques for the industrial scale production. Most reported processes at present require fine compounds of iron, cobalt or nickel as catalyst precursors and several steps of preparation procedures; here we introduce a cheap and robust route toward industrial-scale manufacturing of carbon nanotubes using bulk iron-containing natural minerals as catalysts. In this approach, fine mineral powders were treated with hydrofluoric acid, and reduced at 450℃ in a hydrogen environment, resulting in clusters of uniform nanoparticles of iron-containing silicates. Large quantity of aggregated multiwalled carbon nanotubes (MWCNTs) were grown from those nanoparticles with outer diameters of about 30nm by chemical vapor deposition of acetylene at 630℃. Among a series of our experiments overall yield of final carbon nanotubes arrives at up to 500%. We also explored advantages of our synthesis system at different CVD synthesis conditions: growth periods, gas flow rates and growth temperatures. The increased weight in the first hour of CVD synthesis arrives at more than 70% in final total weight. At up to 900℃ and down to 500℃ there is still MWCNTs synthesized. The acetylene flow rate of more than 4 standard cubic centimeters per minute (SCCM) is not obvious to increase final product weight. The information from our tries implies that the synthesis processing does not need the exact sensitive condition and the expensive laboratory equipment and the complex catalyst preparation procedure.