Texas - Value of Mineral Rights?

Why would someone out of the blue offer a large amount of
money for my mineral rights, when I’ve never been offered
anything before.

what is considered “large?” What does the number come out per acre? It could be someone speculating or potentially a trend of more offers coming in.

Where are your minerals? That will help answer the question. If you are in South Texas, it could be the Eagle Ford Shale…