Most useful high explosives, like ammonium nitrate, are enormously violent ... once they're triggered. But they will remain seemingly inert when beaten, burned, variously punished—until the particular shock required comes along.... any years had passed since the original country rock had been broken, cut and set, to form solid pavement for the courtyard at Opertal Prison. And over those years the stones had suffered change as countless feet, scuffing and pressing against once rough edges, had sm