Many rumors abound regarding the manufacture of salt. It is of critical importance to have accurate information to determine if there is an issue of Bishul present or if it was cooked as part of its processing and is only Bishul Achar Bishul.
The following is comprehensive research conducted by the OU on the topic and some of my related comments and observations.
For those learning the Sugyos of Grama and especially how they relate to modern electronic devices, the following patent application for the Shabbos elevator in Shaarei Tzedek hospital is very enlightening.