We are talking of mosaics that were made by teams of artisans created on plaster. It was common to use semi-precious stones that could be carefully placed by an artisan so that they would better reflect the light, if slanted a bit by design, some of the tiny mosaic semi-precious stones would catch and reflect light.
In the Wealth of Nations, Smith writes about an "invisible hand." the best answer to describe this invisible hand is A) a guid that ensures that people produce the things that society needs. This idea was the basis for market capitalism.
