If you cannot distinguish between a man-made diamond and a natural one when looking at the two, you are not alone. The majority of the differences between the two types of diamonds are either intangible or cannot be seen with the naked eye.
Natural diamonds are formed by the intense heat and pressure at the Earth's mantle--a process that can take billions of years. Man-made diamonds, on the other hand, are produced in a period of several days in laboratories through the use of chemical vapor deposition or artificial high pressures and temperatures.
Both man-made and natural diamonds have the same crystalline carbon structure and chemical properties, making them the hardest substance on Earth.
Two visual characteristics particular to man-made diamonds are not present in naturally occurring ones. Man made diamonds give off a fluorescent orange glow under UV light and bear a GIA (Gemological Institute of America) inscription reading "Laboratory Grown."
Natural diamonds are more expensive than man-made ones because naturally occurring diamonds are rarer. As a result, man-made diamonds can be priced at anywhere between 20 percent and 90 percent of the price of natural ones.
Diamond mining, particularly in African countries, is surrounded by political controversy as a result of the corruption and violence attributed to the practice. Man-made diamonds are not associated with any such stigma.