Pandanus candelabrum. It might sound like a mouthful, but this thorny, palm-like plant is about to get a lot of attention. Geologist Stephen E. Haggerty of Florida International University has noticed that this picky plant only likes to grow in the best, most expensive soil. That is to say, soil that contains diamonds. The paper describing this intriguing find has been published in Economic Geology.
This choosy plant has only been found on top of kimberlite pipes: mineral-rich geological formations that bring up material, including diamonds, from Earth's mantle layer. These fertile underground structures are leftover scars from ancient volcanic eruptions. Each one is shaped like a champagne flute and filled with a fertile cocktail of minerals such as potassium, magnesium, and phosphorus. “It sounds like a very good fertilizer, which it is,” says Haggerty. Perfect for a plant with expensive taste.
Haggerty associated Pandanus candelabrum with diamonds when he was searching for these kimberlite pipes in Liberia. He was dredging swamp soil in search of minerals that would indicate the presence of a kimberlite pipe below. While dredging, he not only discovered a new kimberlite pipe, 50 meters across (164 feet) and 500 meters (1,640 feet) long, but he also noticed that one particular plant was only found growing above these pipes: the Pandanus candelabrum.
A grove of Pandanus candelabrum, which appears to grow only in diamond-bearing kimberlite soils / Stephen Haggerty
“It’s a brilliant observation, particularly in a heavily forested area that’s difficult to do exploration in,” says Karin Olson Hoal, a diamond geologist at the Colorado School of Mines. It's not surprising that the correlation has only been discovered now.
Haggerty will continue to evaluate the soil in West Africa in an effort to diagnose which kimberlite pipes are worth mining for diamonds amongst other minerals. He also wants to understand how the plant exchanges nutrients from the lush soil.
The overgrown forest makes finding this plant a tough task, so efforts will be made to try and spot this plant from aerial and satellite images. This could help West African countries locate diamond deposits, which could mean fantastic revenue from diamond mining. An added bonus comes from the fact that kimberlite pipe mining is less destructive to the environment than, for example, open-pit copper mining. The kimberlite pipe's column shape means kimberlite mines are narrow and damage the local ecosystem minimally.
The future also means looking into the past: The soil from the kimberlite mines will help geologists figure out what the heat and pressure conditions of Earth's mantle were like 150 million years ago, the same time that a rift opened between Africa and South America to create the Atlantic Ocean. The diamonds themselves are windows even into the ancient past—some are around 3 billion years old. The minerals trapped inside the diamonds may hold clues to the conditions that the diamonds experienced deep inside the earth.