Any crystal that is a 5 or below on the Mohs hardness scale should not be put in water. If left in water for an extended period of time, these crystals will dissolve or crack. Some harder crystals should be kept away from water as well. These include crystals that contain minerals that can rust or can release toxins into the water. Selenite, Malachite, Calcite, Fluorite, Rhodochrosite, Hematite, Jade, and some others are the ones that shouldn’t be in touch with water.
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