If you've never seen or used magnesium powder... It's white powder. Yeah, it looks like coke. However, if you want to shock some people and be entertained for a minute, spill some on the table and proceed to try to scrape it in a little pile to clean up. Chances are (for me at least) it will end up in a line and your boss will walk around the corner to your desk.
Incredibly grateful that my boss has a great sense of humor. I guess it probably didn't help that I was giggling like a child about the fact that it looked like I had a line of coke ready to go on my desk on government property. It was magnesium! I've never done drugs. Scouts honor.
Lesson learned: bring pre-mixed magnesium lemonade to work.