We stopped in on a whim, and are so glad we did!
It was the end of low season (Mother's Day weekend), so it was a light group (just 4 adults on our tour). The tour guides are also miners (only tours, or mining, can go on at once -- so if you're on a tour, they aren't actively mining), so they're not what you'd get at Disneyland, but you'll get authenticity. I went with my husband, who is claustrophobic, but since this didn't involve crawling into tight spaces, he was fine. Can't speak for how it might affect someone who doesn't deal well with not being able to see daylight.
We really appreciated the chance to see and hear some of the equipment that was used in the early days of mining. It was money well-spent, in our opinion. And yes, the elevator that takes you down to the level of the tour is tiny (the 4 of us plus our tour guide was plenty cozy), but again, it adds to the understanding of what the miners actually went through.
Wear shoes that you don't mind getting a touch muddy (depending on the amount of moisture in the tunnels, you might be stepping in some very shallow puddles), and bring a medium jacket (it's about 50° F in the tunnels)
Also, we spoke with one of the owners, and she said that construction on permanent toilets for visitors is in the works, so the porta-potties are short-lived. But please remember, you're in a very small town, not a full-fledged resort, so lots of things you might expect in other towns, you may not find here. Go with the flow, enjoy the characters you meet, remember the history of the town, drink lots of water, and enjoy!!
If you own or manage Mollie Kathleen Gold Mine, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.