Cost of processing is also a factor. Since natural stone has been used as a building material for thousands of years in many locations overseas, those areas have a long-established system for quarrying and processing these stones which is efficient and economical.
Sources of natural stone with desirable qualities are found all over the world, in many different locations. Some sources are better than others due to the stones’ appearance, hardness, and other qualities. Therefore, stone may be quarried in China, India, Africa, South America, and some does come from within United States borders.