Which diuretic remains effective when creatinine clearance drops below 25 ml/min?

Loop Diuretics

These are diuretics that exerts effect on the loop of Henle.  They are primarily used in heart failure, hypertension and edema. In contrast with Thiazides, loop diuretics are more  effective in patients with abnormal kidney function. Loop diuretics inhibit the magnesium and calcium reabsorption in the thick ascending limb of Henle. Loop diuretics is highly protein bound. It has volume of distribution that is limited. This causes the diuretics to be secreted in the convuluted tubules  to exert its function.

C. gemstones they are the only non metallic mineral from the list.