What is the difference between natural diamonds and lab grown diamonds?

On a scientific level, natural diamonds and lab grown diamonds are the same - chemically, physically, and optically. The only difference between them is that one is mined from the depths of the Earth, and the other is made in a laboratory. 

Because of this fact, the Diamond Foundry asked that the FTC remove “natural” from the diamond definition. It contended, “[t]he fact that diamonds exist in the soil of Earth” is “not a necessary attribute.”

The Commission agreed, and therefore eliminated the word “natural” from the diamond definition in the final Guides.

The FTC’s definition of “diamond” now reads as: “A diamond is a mineral consisting essentially of pure carbon crystallized in the isometric system. It is found in many colors. Its hardness is 10; its specific gravity is approximately 3.52; and it has a refractive index of 2.42.”

A Brief History on Lab-Grown Diamonds:

When the Commission first used this definition in 1956, there was only one type of diamond product on the market – natural stones mined from the earth. Meanwhile, man-made diamonds suitable for industrial use were first produced in a laboratory in the 1950s. While gem-quality diamonds were produced in a laboratory for the first time in 1971. Since then, technological advances have made it possible to create diamonds in a lab. However, it wasn’t until the mid-2010s that colorless laboratory-grown diamonds entered the gem and jewelry market in commercial quantities. These stones have essentially the same optical, physical, and chemical properties as mined diamonds; thus, they are diamonds. 

How are lab grown diamonds made?

Lab grown diamonds are made by a high pressure, high temperature machine (HPHT) that mimics the pressure of the Earth and the temperature of the Sun. Simply put, the HPHT method simulates the natural process of a diamond created in the Earth by leveraging the same pressures and temperatures.