Natural vs. Man-made
Of all the natural stone, granite stands out head and shoulders above the rest—in every technical characteristic, and virtually every application requirement. Since the world is a ball of granite, it is available locally everywhere, and a modern industry stands ready to supply it in any form you desire. Certainly, other natural stones offer choices, but always with concomitant lesser performance
In recent years, there has been a concerted effort by vendors of man-made materials to enter the markets traditionally served by natural stone. These man-made substitutes are being promoted by some very respectable companies such as Owens Corning and Dupont Chemical.
Their promotional efforts, including print advertising and brochures, are very careful not to mention they are man-made. They risk confusing the consumer by referencing attributes of their products without mentioning the drawbacks. They are trying to be look-alikes without being equivalent.
What is their selling point? Price! These man-made substitutes are concocted in a laboratory from low cost raw materials and presented to the market as a lower priced "stone". But they are not stone, they are plastic or concrete—with all the limitations of plastic or concrete. Their biggest failing is that they don't last. They can deteriorate due to environmental forces, crack and fail due to pollution, fade due to sunlight, and do not provide the low maintenance, vandal resistance, high wear resistance and strength of granite.
They can be lighter, as most cheap substitutes are. That's one way to be cheaper. Initially, they may visually appear to be satisfactory, particularly from a distance. But it is usually not long before they become less attractive, even shabby and ultimately have to be replaced. For many builders, the temptation to build "cheap" is great, but you are reminded of the many man-made substitutes that didn't perform well, and ultimately, failed the test of time.