Is lava rock safe?

[Beasty_Artemis]

So I was thinking about using the idea for entertaining my tortoise using a piece of beach coral, and poking salad greens in the little holes. Loved that inspiring idea, by the way!

So I just noticed a fist sized lava rock on the ground, and I was wondering if anyone had any ideas if it would be safe in a tortoise enclosure....? Not that little red kind.
I know lava rocks can have a metal content....
???

 

[Speedy-1]

I am no expert , but I would be concerned about my tort biting off a chunk and eating it . Which could cause all sorts of painful , expensive problems !

 

[enchilada]

as long as its not molten lava

 

[HI Tortoise Rescue]

It better be safe, 'cause that's about all we have out here! Unlikely to fragment, as the grains are tightly-bound, but I'm not sure whether you've found lava in Portland. There are other stones called breccia that look like lava-rock, but can fragment, so please see if your fingers can break off any pieces before giving it to your tortoise.

Ken