Abstract: A mold is provided for forming a concrete column having at least one recess formed therein, as molded. The mold includes a tubular housing having an inner surface and a recess form having an inner and an outer surface. The recess form is mountable in the housing at a desired location on the inner surface of the mold housing. The recess form is preferably generally a ring The ring's outer surface corresponds to the shape of the housing's inner surface so that, when the ring is mounted in the housing, there are substantially no gaps between the outer surface of the ring and the inner surface of the housing. The ring has a slice through it, so that the ring may be expanded and pried out of the groove or recess molded in the column once the cement has set. Preferably, the slice is off-set from a radial line drawn through the ring. The ring is secured in place in the mold using screws.

Abstract: The invention provides surface elements such as tiles or panels consisting of a thin lamina of natural stone bonded to a backing consisting of a multicellular paper core material of substantially greater thickness than said lamina which at least on the side remote from the stone lamina has a skin of tenacious sheet material bonded thereto. The resultant composite element is extremely rigid, light and cheap to produce in comparison with solid stone and may be cut into any desired shape and used as a substitute for solid stone, but with the advantages of lightness, strength and low cost thus enabling such surface elements to be used for many purposes where the use of solid stone would be economically or practicably prohibitive.