In Romania, there is a region filled with strange stones called trovant, which have the ability to expand and grow like… mushrooms after rain.
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The small town of Costesti in Romania is home to expanding stones known as trovant. For a long time, these stones have piqued the curiosity of locals due to their unusual shapes and their ability to generate, grow, and move like living beings.
Trovants come in a variety of sizes and shapes; some can fit in the palm of your hand while others tower over a person, with some even reaching sizes of up to 4.5 meters. Among the more than 100 trovants recorded at at least 20 locations, a few stones have been excavated after the sand surrounding them was mined.
The strange stones in Romania, which can expand and grow like mushrooms after rain, represent a mysterious phenomenon that has attracted significant scientific interest. These stones are linked to a geological phenomenon in the area.
This stone is called Trovant.
In fact, some trovants are firmly anchored to the ground beneath them by a solid stone base, like the “Old Ladies” stone in Ulmet. Their unusual swelling shape originates from ancient origins.
This type of stone is found in the village of Costesti in Romania. The term trovant means “cement sand.” This stone is formed from a type of sand that appeared millions of years ago on Earth. Indeed, the seismic activities that created these strange stones occurred around 6 million years ago.
The stones grow in a strange manner.
It is astonishing that during and after every rainfall, the Trovants in Costesti sprout up like… mushrooms. The stones swell in a peculiar way. Trovant stones only grow when it rains. Normally, they are just 6 to 9 mm in size, but when they come into contact with water, they can expand to between 6 to 10 meters. Some stones can even move. When cut in half, their insides reveal rings similar to those of a tree trunk.
After heavy rains, the stones begin to “come to life”.
Inside the trovants are hard stone cores, while the outer layer is composed of sand. However, the phenomenon of the trovants swelling has been explained by some scientists as being due to a high mineral content beneath the stone’s outer layer. When the stone’s surface gets wet, this mineral begins to exert pressure on the outer sand layer, causing the stone to start expanding. The stones can take on different small shapes: oval or bumpy like small pimples appearing on the surface of the stones. This is a form of cementation with sedimentary sand particles or stones bound together by calcium carbonate. “Some are made from sandstone, while others are made from gravel. In geological terms, they can be referred to as grinding stones and conglomerates“, said Florin Stoican, a representative of the Buila-Vanturarita National Park.
People refer to them as growing stones.
Researchers have found no significant difference between Trovant and the surrounding sand. Therefore, they suspect that the spherical shapes were formed due to prolonged and unusual seismic activity during the Middle Miocene. Shock waves emanating from the Earth compacted the sand sediments and condensed limestone cement to create spherical stones.
Over time, these elements have eroded the loose sandstone surrounding them, exposing denser layers of stone.
When exposed to heavy rain, their calcium carbonate may dissolve and gradually shape the outer contours of the stones over time. There is not much documentation on this process, but it is believed to occur at a rate of only about 4-5 cm over more than 1,200 years.
The surrounding sandstone layers show signs that this area was an ancient marine environment when the fundamental rocks and sediments were formed, and fossils of bivalves and gastropods can be found in some Trovants.
