I have had a small bottle of Johnson & Johnson powder chemically checked on two occasions.
Okay, but the question was what is allowed through security. Powders are allowed. Following the TSA rules doesn't mean that your allowed items won't be tested or swabbed for explosive residue. I assume that after being tested, you were allowed to bring your powder through.
I've posted before, about one time when I was doing carry on only. They ran my carry on through a couple of times and finally asked if it was mine, and said they needed to search it. The TSA agent picked up a bag of sealed, labeled bath salts, shook them, opened them, smelled them, ran his little cloth covered wand thingy through them, and finally ran his gloved fingers through them. I laughed and told him they were just bath salts (about a quart). He actually glared at me, told me he wasn't sure they were allowed, and had to call a supervisor. When the supervisor came over, he took one look at them, gave his agent a disgusted look, said they were fine, and to let me go. Instead of apologizing, the DFW TSA agent actually glared at me, said he was going to let me through this time, but I had 'better not try to
sneak something like that through again'.

What was funny, is that I had decided at the last minute that I didn't really need a checked bag and was going to do carry on only, so had rapidly switched things around just the night before. Directly beneath that bag of bath salts he was so concerned about, I had a small packing cube that had a zip lock bag with a tiny bottle of cleansing oil, mascara, and a lip gloss, mixed in with some other small items. I had forgotten to put them in the 3-1-1 bag. He was so concerned about those bath salts that were legal, that he missed three items he should have caught and would have, if he had simply glanced down at it, since the top of the packing cube was mesh. Those bath salts were sitting directly on top of that little packing cube.

