April 05, 2023 3 min read

Gem-quality diamonds are regarded as one of the most precious and sought-after materials on Earth. Their formation process, which requires specific and important components, significantly contributes to their rarity and value. In this article, we will delve into the details of the diamond formation process, the unique properties of diamonds, and why they are so special. As you gain a deeper understanding of the extraordinary nature of diamonds, you will appreciate even more the beautiful gems that you see every day.

The Role of Temperature and Pressure in Diamond Formation

Temperature and pressure are fundamental elements in the formation of any substance, including diamonds. For instance, water can freeze into a solid state under very cold temperatures, but ultrahigh pressure can also cause it to solidify. The combination of temperature and pressure is what causes diamond's atoms to link together in the unique way they do, making diamond the hardest substance on Earth.

The History of Diamond Research

In 1772, French chemist Antoine-Laurent Lavoisier conducted an experiment that would become a cornerstone of our understanding of diamonds. He burned a diamond in an oxygen-filled glass jar and observed that the only byproduct was carbon dioxide gas. Years later, English chemist Smithson Tenant built upon Lavoisier's findings, proving that diamonds and charcoal were composed of the same substance - carbon - but in different forms.

Diamond and Graphite: Different Forms of Carbon

Diamonds and graphite are both made only of carbon, yet they exhibit very different properties. Graphite is soft and slippery, making it an excellent lubricant and a key component in pencils. In contrast, diamonds are the hardest mineral substance on Earth. The difference between these two materials lies in the arrangement of their carbon atoms and the pressure and temperature conditions during their formation.

Earth's Layers and Diamond Formation

The Earth is composed of three main layers: the crust, the mantle, and the core. Diamonds form in very limited areas of the Earth's upper mantle, between 90 miles and 120 miles beneath the surface, where the ideal temperature and pressure conditions exist. The best conditions for diamond formation are found under large, geologically stable parts of the crust called cratons, which make up the interior portions of the continents.

Diamond's Source Rocks: Peridotite and Eclogite

Diamonds form in two types of igneous rocks: peridotite and eclogite. These rocks have different mineral compositions and provide their own supply of carbon. Peridotite is an ancient rock that releases its carbon as it melts in the Earth's inner heat, while eclogite is a younger rock that releases its carbon through subduction, a process where crustal plates collide and one is forced under the other.

Diamond Transport and Delivery: Kimberlite and Lamproite

Diamond deposits are found in two types of rock: kimberlite and lamproite. These rocks are not where diamonds form, but they carry already-formed diamonds to the surface through a process called emplacement. As kimberlite or lamproite magma rises through deep fractures in the crust, it can pick up and carry diamonds, eventually erupting through the surface and forming a pipe.

Arrival at the Surface and the Rarity of Diamonds

Once the kimberlite or lamproite reaches the surface, it solidifies, and the erupted material falls back into its pipe, along with its diamond cargo. While there are thousands of known kimberlites worldwide, fewer than 1,000 of them contain any diamonds, and only about 50 are economically viable to mine. This makes gem-quality diamonds incredibly rare and precious.

Understanding the intricate processes of diamond formation and transportation to the Earth's surface reveals the extraordinary nature of these gemstones. The rarity and beauty of diamonds are a testament to the incredible geological processes that create and transport them. The knowledge of these processes not only enriches our appreciation for diamonds but also highlights their rarity and value in the world of gemstones. As you admire the dazzling array of diamond jewelry, remember the incredible journey that these gems have undertaken from deep within the Earth to the surface, making them truly special and unique.