This card shows a young woman observing some stalactites in the Cave of the Mounds.
Photo by Diemer, Madison, Wisconsin
Regrettably, the black and white photo, combined with the limited lighting in the cave, result in a photo that is not particularly evocative of the name. As a result, it is not clear why this is the Gem Room, other than the fanciful imaginations of the owners and marketers. The description states simply:
Gem Room – Cave of the Mounds, Blue Mounds Wisconsin
The woman’s attire indicates this photo is from the 1940s.