A method of making a cementitious product that resembles a naturally found item is disclosed. The original item, for instance a piece of petrified wood, is used as a guide in mold-making and subsequent decoration of the cast product. The mold is made by applying coats of resinous composition to the exterior of the original product and stabilizing the coats by securing an open-weave fabric between the coats. The resultant flexible mold is used for pouring of a cementitious mixture and forming a cast that closely resembles the appearance and textural characteristics of the original item.