We do our small items Costco shopping during US weekend trips since the New York City stores are not convenient for us to reach. Returning from our Minneapolis weekend I had 3 Himalayan pink salt grinders earmarked for family in China.
I am not a chemist though figured salt might attract security attention. Indeed it does. The TSA scanners flagged my bag for secondary.
TSA did the usual swab test, which was not the end of it. So concerning is salt that I had to break open the packaging on each for individual testing of the crystals, ruining them as gifts. At this point, while the test was being handled as a training session for a new agent, the supervisor suggested that in the future I either put my salt in checked baggage or only carry a few packets.
I did not find any TSA statement on salt, though there is this attempt at humor with regard to powders.
There you have it, 3-1-1-packet is the rule.