 Given the information in the article, what is the purpose of a Geiger counter?
Still, one clue is as good as another when it comes to hunting uranium ore, I guess. When carefully controlled, the radiation stored up in such isotopes was used in many beneficial ways. “Anything else, Mom?” he asked, returning to the house and getting the Geiger counter out of the closet. At various rock mounds and outcroppings, Eddie switched on the Geiger counter. It was in the air itself, caused by mysterious and ever-present cosmic rays, so there was always a mild background count when the Geiger counter was turned on; but to mean anything, the needle had to jump far ahead on the gauge, and the clicking through the earphones had to speed up until it sounded almost like bacon frying in a hot skillet.
 To measure for radiation.
 To measure rock formation patterns.  To measure for radiation.  To find hidden rocks.  To measure gravity.