Natural Marble and Natural Granite, being used in civil construction, are finite resources not perpetually available. There have been attempts to match the attributes of natural marble and granite by artificial processes and at less expense. Though these products closely resemble natural stones, the processes used in manufacturing these articles are slow, and they are difficult to recycle due to the fact that they are made using a combination of different materials. The present invention provides a method for preparing composite board in polypropylene and digitally printing & coating it externally to provide aesthetics and required hardness. The method comprises corona treatment; applying and drying a primer; applying and curing base coat on the dried surface; sanding of the board using fine emery boards; digitally printing and curing the sanded board; application and curing of a primer; and coating and curing to gain surface hardness, abrasion resistance, scratch resistance, fire resistance and gloss.