What kind of rock is this being eaten by a rock-eating worm? The New York Times article This Creature Eats Stone. Sand Comes Out the Other End. describes the shipworm Lithoredo abatanica, an organism that appears to "eat solid rock".

It links to the item in Science This rock-eating ‘worm’ could change the course of rivers which then links to the YouTube video Snippet: Shipworms that eat rocks.

The video shows how easily this rock can be split apart.

The rock was taken from the bottom of the Abatan River on Bohol Island, in the Philippines.

Question: Is it possible from the images, descriptions, and video to say something about this rock? Is it a kind of sandstone? It looks fairly loosely held-together and porous.



Images from NYTimes:



above: Lithoredo abatanica, from inside a piece of rock. CreditM arvin A. Altamia and Reuben Shipway (click for full size)

below: Two large burrows in rock made by shipworms. Credit Marvin A. Altamia and Reuben Shipway (click for full size)
thank you for your interest in the article. I'm the lead author on this paper (Shipway) and I happened to come across your post when looking through all the media stories on this animal. 

To answer your question; yes, you're right, the rock is a calcareous sandstone. It was easy to split, partly because it is a naturally soft rock and partly because the shipworms had weakened the structure.

Hope that answered your question.