About the same as a bar of gold in Fort Knox, a stack of $100 bills, or a few bitcoin. This is from "Debt, the first 5000 Years" (David Graeber, 2014)
It should be more expensive than the rock from land, and cheaper than the rock that drops from outer space.
The book "The Bitcoin Standard" discusses the Rai stones as primitive money. Fascinating story I haven't finished the book, yet, but so far it's a been a great read
If the rock is found to be very old, like around 1000 years, then it might have a good value. Basically it depends on the quality of the rock.
Many countries have made bitcoin legal which means it is used as normal money. But that doesn’t mean that every country would do that. Decisions are taken after studying every aspect.