Humphrey's spiral

Humphrey's spiral

[′həm·frēz ‚spī·rəl]
(mining engineering)
An ore concentrator consisting of a stationary spiral trough through which ore pulp gravitates; heavy particles stay on the inside and lighter ones climb to the outside.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.