Wed 25 Jan, 2017 03:06 pm - Interesting. The rock is not entirely covered by that "crust" as you can see in this image: https://pbs.twimg.com/media/C3C5jIPVcAAX6VE.jpg
I thought all lava rock was really porous.... (view)
Wed 25 Jan, 2017 09:51 am - I have a stone that appears to have a crust adhered to it and am very curious about what it might be. Any ideas? Here's a photo:... (view)
