Ah, the persistent calcite vs. quartz debate! So this isn’t a definitive test to determine just ANY clear mineral; there are plenty of clear minerals that would perform differently on this one simple test. But, if someone tells you “hey, this is EITHER a quartz or a calcite, can you tell which?” this is one indicator test. If you want one quick visual test that would help, gemmy calcite is so doubly refractive that it will often show doubled images, but you might have to test it at a few differe

Why fire ants are so good at survival