score:4
The 'LAG' restrictions enforced throughout much of the world cover Liquids, Aerosols, and Gels. Whilst the definition of these can be a little vague (is Peanut Butter really a Gel?), dried "salts" fairly clearly do not fit into any of these categories.
I have traveled with bath salts > 100ml/100grams in my carry-on bags in the past and have never had a problem. On one occasion the airport security staff did ask to see them as they were not able to determine from the X-ray what they were, but once they confirmed what they were then I was let through without any issues.
The US TSA "Can I Bring" website doesn't have a specific entry for Bath Salts (which is a good sign, as if they were disallowed it most likely would), but does have "salt" which is allowed with no size/volume restrictions.
Just as a warning, be aware that "bath salts" is also the street name for an illegal class of Synthetic cathinone drugs. They have this name because they have a crystalline form that resembles normal bath salts.
Upvote:1
There was no problem with 1kg magnesium flakes for cabin baggage. Security staff didn't know about the restrictions.