. . . . after a hot day in the desert when I returned to her parents' home with a very painful heatrash in an embarrassing location.
'Washing up' before dinner I noticed a small dish with powder which I mistook for talcum (how could a geologist ever do that??*) and applied generously to the afflicted parts.
So sorry, . . . . it was laundry detergent! ..
* Toronto Girls Can Flirt And Other Queer Things Can Do
that's why I had to go to Toronto to investigate
MOH's Hardness Scale: