JCZ (acronym), for ‘Jacobs-Cowperthwaite-Zwisler’. JCZ3 (abbreviation), for ‘equation of states for detonation’. Jeffrey crusher, whizzer mill, see ‘swing hammer crusher’. jet corer, consists of a length of pipe which is lowered from a vessel in order to obtain sam-

ples. High, velocity water is pumped through the pipe and the jetting action of this water issuing from the lower end of the pipe very effectively cuts a hole in the unconsolidated overburden sediments. Once at bedrock, the pipe is rammed into the rock with sufficient force to obtain a plug of about 50-100 mm in length. Mero, 1965.