thaumaturgy kit

"It means I need something from my kit. Be right back." I went outside and down to my car, where I kept a fisherman's tackle box. I snagged it and went back up to the dead woman's bedroom.
"That's new," Murphy said.
I set the box on the floor and opened it. "I've been teaching my apprentice thaumaturgy. We have to go out to the country sometimes, for safety's sake." I rummaged through the box and finally drew out a plastic test tube full of metallic grains. "I just tossed things into a grocery sack for the first couple of weeks, but it was easier to put together a more permanent mobile kit."
"What's that?" Murphy asked.
"Copper filings," I said. "They conduct energy. If there's some kind of pattern here, I might be able to make it out."


White Night, Chapter 1, Page 7