Rock inclusion

Asked April 21, 2019, 1:50 PM EDT

This rock was found on a beach British Columbia, Canada. The circular objects appear at the side of the stone so i presume they are round and not tubular. The circular objects are hard and do not appear to be surface lichens or organic. The black granules are softer may be organic but leave craters when scraped free.

Outside United States rocks and minerals geology

1 Response

Nice river cobble! Actually, you were correct in your initial identification of the circular features. They are a form of lichen. The cobble appears to be granitic in texture. New science is emerging regarding the age dating of landslides and glacial advances, based on lichen growth. There are also applications for archaeology. https://en.wikipedia.org/wiki/Lichenometry

The identification of the individual lichens can be challenging. Lichens are part of the weathering cycle for rocks.
Good question!!