The person alleged to have owned the mine apparently does not think it's a rumor

"Well, according to Errol Musk, the unsurprisingly eccentric — and in one major way, extremely creepy — father of Elon, the mine definitely exists. And come to think of it, he'll take that Dogecoin, thanks!

"When I read that, I wondered, 'Can I enter, because I can prove it existed," Errol told The Sun in a new interview, referring to his son's Dogecoin tweet. "Elon knows it's true. All the kids know about it."

https://futurism.com/elon-musk-dad-emerald-mine

So what?

From Snopes:

A story about Musk's father once owning an emerald mine evolved into a larger rumor that had no evidence to support its central claim.

So what? The person who is accused of owning the emerald mine says they owned the emerald mine. That's at least some evidence that its true.