The Cheapest Diamond in the World

Introduction

Diamonds are known as one of the rarest jewels in the world. The factors that determine the price of diamonds are known as 4 “C”: Carat (weight), Color, Clarity, and Cut. Considering these 4Cs, a typical one-carat diamond ring costs about $7000. In addition, the world's most expensive diamonds can reach as high as $65M. As a result, many consumers are now opting for 'lab-grown diamonds' produced in laboratories, as a cost-effective alternative to expensive natural diamonds, and recently, a South Korean research team has developed a new technology to produce synthetic diamonds at the lowest cost in the world.

Why are diamonds so expensive?

Diamonds and pencil lead are essentially the same substance: carbon (C). Considering the environment in which diamonds are formed, it is understandable why there is a huge difference in the price of the two items although they are formed in the same substance. Diamonds are created in the uppermost layer of the mantle, located 140 to 190 km below the continental crust. This depth is crucial; any deeper or shallower depth is not acceptable. Diamond crystals form over millions of years under pressure conditions of 45 to 60 kilobars (thousands of times the atmospheric pressure) and temperatures of 900 to 1300°C. If it is deeper than the uppermost mantle layer, the temperature is too high for carbon, causing carbon to turn into liquid; shallower areas lack sufficient pressure, resulting in the formation of graphite instead of diamonds.

Diamonds formed in such deep locations can only reach the surface through volcanic eruptions. The rocks from the uppermost layer of the mantle, where diamonds are found, are pushed up together with magma. When the uppermost mantle layer emerges at the surface, it solidifies into a rock known as "kimberlite,”  and people mine the crystal of diamond in the kimberlite.

The mining process is also challenging. To extract natural diamonds, the ground must be dug 3 to 4 km deep, and an enormous amount of water is used to wash away the soil. It takes about 500 liters of water to extract one carat of natural diamonds.

What is a “lab-grown” diamond?

The popularity of "lab-grown diamonds" has surged due to barriers posed by high prices and concerns about environmental pollution. Lab-grown diamonds are different from the original synthetic diamonds. Unlike synthetic diamonds, which merely mimic the appearance of diamonds, lab-grown diamonds are identical in composition to natural diamonds. They are created by simulating the high temperature and high-pressure conditions under which natural diamonds grow in the Earth's crust, gradually adding carbon to increase their size.

Lab-grown diamonds can be produced in a laboratory in about 2 to 4 weeks without the need for the entire planet's help. Their price is around 10-20% of that of natural diamonds. Unlike synthetic diamonds, they can also replicate the color of natural diamonds. While the price of natural diamonds continues to decline, the lab-grown diamond market has experienced rapid growth, expanding more than sixteen fold in the past five years.

Low-pressure “lab-grown” diamonds

A recent breakthrough by a South Korean carbon science team has garnered significant attention as they successfully synthesized diamonds without the need for high-pressure conditions. The research team developed a method to synthesize diamonds at 1-atmosphere pressure using a liquid metal alloy. This breakthrough challenges the conventional paradigm that diamonds can only form under high-temperature and high-pressure conditions.

Typically, carbon atoms bond with three surrounding carbon atoms, forming SP2 bonds. Carbon materials with SP2 bonds, like graphene, exhibit a hexagonal honeycomb structure. In contrast, diamonds have SP3 bonds, where each central carbon atom is bonded to four surrounding carbon atoms, creating a tetrahedral structure that repeats in all directions. To convert standard carbon materials into diamonds, SP2 bonds must be transformed into SP3 bonds, a process that is quite challenging.

In this study, the liquid metal alloy played a crucial role in facilitating this bond transformation, enabling diamond synthesis under low-pressure conditions. This research opens new possibilities for diamond synthesis and holds potential for various industrial applications.

Benefits of synthetic diamonds

These synthetic diamonds offer an opportunity for people who were not able to afford to buy diamonds due to their high price. Moreover, these new technologies also contribute to the protection of the Earth's environment. In addition to their commercial value, synthetic diamonds have the potential to be applied in future fields such as nano-sized magnetic sensors or quantum computers due to their adjustable size and weight.

Reference:

• https://www.freethink.com/science/synthetic-diamonds

• https://www.sciencenews.org/article/diamonds-extreme-atmospheric-pressure

• https://www.science.org/content/article/diamonds-grown-without-extreme-pressures