@matteo-di-angelo @lcone Matt, your chemical tests are spot on for Dolomite. In the cases here (Lee’s samples and mine) the crystal shape is the dead giveaway. These crystals exhibit a form not seen in Calcites. They are very thin curved rectangular shapes – kind of like a potato chip that is rectangular rather than oval. The crystals lining the brach have been shown to be Calcite by tests like yours. I attached a cropped photo of the one I sent earlier to show (hopefully) the curved crystal shape of the Dolomite.