One came out of the ground, one from the laboratory environment. Unfortunately, consumers rarely understand this archaic definition.
Natural gemstones are crystals that have formed deep in the earth by heat and pressure.
Stones from Colombia can be separated from Brazil, and those two locations from Africa. No more obvious are the clues in a Chatham stone. Just as man provides the nutrients and controlled environment to help grow a cultured pearl, Chatham provides the natural elements and controlled environment to grow crystals. The culturing starts on a round ball surgically implanted in the oyster's mantel tissue. The culturing of emerald, as one example, starts from a thin slice of natural emerald or beryl.