Diamonds and emeralds are two of the most coveted and expensive gemstones on Earth, but have you ever wondered which is rarer? While the answer might surprise you, it’s not as simple as comparing the number of known deposits.
Emeralds are rarer in terms of known deposits. According to a 2019 review in the journal Minerals, there are only 49 known emerald deposits worldwide. In contrast, there are about 1,000 rock formations containing diamonds, although only 82 are actively mined, according to a 2022 article in Reviews in Mineralogy and Geochemistry.
However, comparing diamond numbers to other gemstones is tricky. The diamond industry is much more established, with international mining companies operating with complex pricing structures and global partnerships to meet demand. Annually, the world produces between 100 and 150 million carats of diamonds, or roughly 22 to 33 tons, according to Natural Resources Canada. On the other hand, emerald production in 2015 from the primary producing countries (Colombia, Zambia, Ethiopia, Madagascar, and Brazil) was estimated between 7,000 to 9,000 kilograms, or about 7 to 10 tons, based on 2022 market research data compiled by the British mining company Gemfields.
Tracking the global production of gemstones other than diamonds is difficult due to the widespread presence of smaller mines across the globe, often operated by smaller companies with limited reporting systems. This makes it challenging to accurately assess the global production of emeralds.
These production figures tell only part of the geological story. Both diamonds and emeralds form through complex processes requiring unique and rare conditions.
The Formation of Diamonds: Deep Within Earth’s Mantle
Diamonds form deep within Earth’s mantle, about 93 to 124 miles (150 to 200 kilometers) underground, making them the deepest gemstones on Earth. They are formed from single crystals of carbon, a process that occurs when changes in pressure, temperature, or chemical reactions cool liquefied mantle rock containing carbon.
However, for diamonds to be accessible to humans, a rare type of volcanic eruption, called a kimberlite, must occur. These eruptions originate from magma located about 100 to 180 miles (170 to 300 kilometers) underground. As the kimberlite travels towards the surface, it can pass through areas containing diamonds, sweeping them up to shallower depths.
The diamond formation and kimberlite eruption are independent events, meaning they are not always connected. Without both occurrences, diamonds would remain deep within the mantle.
The relatively even distribution of diamonds within kimberlite formations makes large-scale mining feasible. Large pits are excavated, blasted, and mined with heavy machinery to extract diamonds efficiently.
Emeralds: A Complex Formation Process
Emeralds are green varieties of the mineral beryl, their color resulting from the presence of chromium and/or vanadium. Beryllium, the primary component of beryl, is concentrated in igneous rocks of the continental crust. Chromium and vanadium, on the other hand, are more common in the upper continental crust.
For emeralds to form, these separate geological environments must converge, allowing beryllium and chromium to interact. This usually happens when rocks containing beryllium or beryl come into contact with sedimentary rocks like limestone or shale. Sometimes, liquefied rock seeps through surrounding rock environments, picking up chromium along the way.
Emeralds are frequently found in collisional zones, such as mountain ranges, where tectonic plates collide, bringing together different geological environments.
Rarer Than Diamonds?
While the conditions required for the formation of diamonds and emeralds are unique, emeralds are considered rarer in terms of human accessibility.
The large-scale mining of diamonds, facilitated by their even distribution within kimberlite formations, makes them more readily available. In contrast, the complex geological formations where emeralds are found are more conducive to smaller-scale, hand-based mining and extraction methods. This limits the overall quantity of emeralds that can be mined.
In conclusion, while both diamonds and emeralds are rare and valuable gemstones, emeralds are generally considered rarer due to their more complex formation process and limited accessibility. Although diamond mines produce significantly more gemstones, the intricate geological journey that emeralds undertake makes them a truly remarkable and rare treasure.