Jade /dʒeɪd/ (from the Greek nephros – kidney: based on the similarity of N. pebbles with a kidney, on which the belief in the healing effect of N. in renal colic was based) is a mineral, a microfibrous variety of amphiboles of the tremolite – actinolite series, Ca2(Mg, Fe)5 Si4O112 ( OH, F)2.