Page 244 - Introduction to Mineral Exploration

10: EVALUATION TECHNIQUES 227

FIG. 10.13 Diamond drill core being examined and stored in a wooden core box. Note the excellent core
recovery. (Reproduced by permission of Diamond Boart Craelius Ltd.)

time lag before cuttings reach the surface. It is contained information is important particu-
estimated that from a depth of 1000 m cuttings larly as during mining some drill locations may
can take 20–30 minutes to reach the surface, be permanently lost.
with the inherent danger of differential settle-
ment in the column of rising water due to dif- Noncore drilling
ferences in mineral and rock-specific gravities In noncore drilling the chips and dust are usu-
and shape. Consequently rock sludge is rarely ally collected at 1- to 2-m intervals, dried and
examined during core drilling. separately bagged at the drill site. After wash-
Obtaining core is expensive so it is sensible ing they are relatively easy to examine with the
to retain it for future examination. How- use of a hand lens and binocular microscope.
ever, adequate and long-term storage involves Samples can be panned so as to recover a heavy
time, space, and expense, but the value of the mineral concentrate. It is a good practice to