Question: What can you tell me about The Growing Stones from Romania called trovants?

Hi!
I’ve been to Romania, but I’ve never seen the Growing Stones. I’d like to because this sounds amazing!
Apparently these rocks were formed about 6 million years ago (during the lte Miocene, which is the period of time that I study in my PhD).
These rocks have a hard stone core and the rest is formed by sand and sandstone deposits which are very porous, which means that they let water go through them. When the water is rich in calcium carbonate it interacts with the sands and it cements them. This creates the outside shell of the rocks, which surrounds the harder core. So basically they are cemented sands that formed a very long time ago. Most of them have rounded shapes, with no sharp corners,
The incredible thing about these rocks is that it looks as if they can grow and multiply. After heavy rain showers some small accretions appear on them. Scientists think that this is a result of these rocks absorbing the minerals from the rainwater, which then creates a reaction with the chemicals that are already in the rocks and generates pressure inside them.
However, as far as I know, these theories are not fully proved.