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This African Plant Leads the Way to Diamond Deposits

A palm-like plant seems to grow only on top of diamond-rich deposits called kimberlite pipes

Diamond crystal on kimberlite from Eastern Siberia (145/Matteo Chinellato - ChinellatoPhoto/Ocean/Corbis)
smithsonian.com

Diamonds are forged about 100 miles below the surface of the Earth where intense heat and pressure turns carbon into shiny gems. Diamonds that have made it to the surface were carried there by intense eruptions rooted deeper than ones the planet sees today. After rocketing upward at 20 to 30 miles per hour, that volcanic material cools into mounds, leaving behind a rocky piles, beneath which stretches a long pipe called a kimberlite. Most diamonds in the world are mined from such kimberlite formations (though some can be formed during meteorite crashes).

Though diamonds aren’t as rare as most people believe, the diamond industry is constantly looking for new deposits. Now a geologist may have found an easy way to identify diamond-rich areas: look for a rare plant that seems to grow only those kimberlites, reports Eric Hand for Science.

Stephen Haggerty, of Florida International University in Miami and the chief exploration officer of Youssef Diamond Mining Company noticed the plant during surveys in Liberia, where the company owns mining concessions. Hand writes:

It has a stiltlike aerial root system, similar to mangrove trees, and rises to a height of 10 meters or more, spreading spiny, palmlike fronds. He says local people use the fronds for thatching their roofs. Working with botanists from the Royal Botanic Garden, Kew, in the United Kingdom, and the Missouri Botanical Garden in St. Louis, he has tentatively identified the plant as [Pandanus] candelabrum, a poorly understood species in a family that ranges from Cameroon to Senegal. He says it could be a subspecies or a new species altogether. Haggerty has confirmed the presence of the plant at another kimberlite pipe 50 kilometers to the southeast, but it does not seem to grow elsewhere.

Plants signaling that something of interest lays below aren’t new in the mining world. People have long known that Lychinis alpina, a small plant with pink flowers, heralds copper deposits. More recently a shrub named Haumaniastrum katagense has been associated with copper as well. Both plants are unique because they're able to tolerate the high copper content in the soil near deposits. Haggarty suspects that P. candelabrum has specifically adapted to grow in kimberlite soils, which contain a lot of magnesium, potassium and phosphorus. The researcher wrote up his discovery of the plants’ unusual affinity in the journal Economic Geology.

The finding could offer a better way to pinpoint new diamond mining sites in the thick jungle. Prospectors are going to "jump on it like crazy," geologist Steven Shirey of the Carnegie Institution for Science in Washington, D.C. told Science. But new diamond deposits are interesting from a scientist’s perspective as well. Shirey points out that the diamonds from mines in Liberia could tell researchers about what the Earth’s mantle was doing when they were formed, millions of years ago. On the other hand, being an indicator for mining operations can’t be good for the plant’s longevity. 

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