Four rough stones ready to tumble! Each stone is approximately 1 inch. This is a soft stone: a Mohs hardness scale of only 3 will require very few days in the rock polisher.
Calcite is sedimentary, a calcium carbonate that precipitates from water. Due to its high calcium content, it will bubble (effervesce) when rinsed with vinegar. In archaeology, calcite is sometimes called alabaster.
A perfect gift for the rock hound in your life. If they don't already have a rock tumbler, you're in the right place. The Science Museum of Minnesota also sells tumbling supplies and equipment.
