A Geostatistical Approach To Operational Sample Design For Ore/Waste Selection In Surface Gold Mining - Introduction And Motivation

The January 1988 issue of Engineering and Mining Journal includes two short articles on blasting practices in surface gold mines (Anon., 1988 ; Carr , 1988). A reader of these articles learns, among other things, that a "12 x 13 ft" blasting pattern is used at the Carson Hill Mine, and a "17-ft burden and 18-ft spacing" is used at Echo Bay Mineral's Borealis operation, while at Mascot's Nickel Plate Gold Mine "ore shots are on a 10 x 10 ft" pattern. Like a new edition of the World Book Almanac, these articles are overflowing with useful tidbits of technical data; but, they never mention why the particular blasting patterns were selected. A survey carried out during the Winter of 1988 at six surface gold mines in the western United States also failed to produce a satisfactory answer. The responses from mine planning engineers to the question "why is your blasting pattern X by Y", reduced to "we use X by Y here because we used X by Y at our last operation, and it worked ok." Certainly, with the available decades of experience and professional practice in blast holes design, rock fragmentation in surface mines has been thoroughly investigated. However, and this is the central issue, fragmentation of the rock is not the primary purpose of most rotary drill holes in surface gold mines. Quoting senior mine engineers from companies operating, three of the richest surface gold mines in the world (AMAX Gold, Homestake Mining, and Gold Fields Mining)