Hello. Here is an image of a crystal that I was given as a gift. I have no information about the item, I initially labeled it as quartz, but I examined the crystal structure and it does not seem consistent with a quartz pattern.
Chemically, quartz is silicon dioxide, and calcite is calcium carbonate. Two simple means of distinguishing them are: 1) Hardness: quartz is 7 on the Mohs scale
