This crystal is tiny, a mm only, but it exhibits the satisfying deep blue colour only copper is capable to produce. This is Callaghanite, copper magnesium carbonate, found at Gabbs, Nye County, Nevada, USA
"Salt wasn’t always shake-able. In the early part of the 20th century, the Morton Salt Company of Chicago added magnesium carbonate to their salt to make it flow. Before that, salt was clumpy and rough, served in little containers (salt cellars) that you’d pinch your serving out of. Of course, if you were fancy, you’d have something like these silver seashells, with accompanying tiny spoons."