While in Paris we traveled to another location that held the promise of gypsum. Parking in the downtown, we followed a trail along the south side of the river keeping our eyes peeled for more white rocks.
I was looking for a white, powdery rock such as we had collected on the other side of the river, but when Reiner said he had found some he handed me something quite different. This rock was hard and it contained crystals (something I hope you can see in the photo I’ve posted). These crystals weren’t a contaminant, as I supposed, but are the crystalized form of gypsum called Selenite. So the rock I was looking at is still completely pure gypsum!