A typical naturally occurring mineral, marine manganese nodule, could be developed as a catalyst for the catalytic chemical vapor deposition synthesis of helical carbon nanotubes by changing the experimental conditions. In the product, a novel one-dimensional carbon nanostructure with triple helices was first observed. The possible origin is briefly discussed. It points out a facile method to obtain helical carbon nanostructures. (c) 2005 Elsevier B.V. All rights reserved.