buttmasterflex

Between halite and quartz, absolutely. Halite and sylvite have the Moh’s hardness of 2, so your keys would scratch both.

Licensed Professional Geologist here, and licking is a totally valid method for distinguishing between mineral hand samples that have very similar properties otherwise. For instance, halite (NaCl, aka table salt) and sylvite (KCl) are isomorphous, which means they have the exact same crystal structure and are very difficult to distinguish using traditional methods. Halite tastes like salt, but sylvite makes your tongue tingle when licked. Our mineralogy professor told is it’s the only reliable way to differentiate the two without actual chemistry analysis.

People are mentioning pyrite. There are also many other examples that all fit into the cubic crystal system. Geology, yo!