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| _Pieces of drill cores Photo by Constantino Figini |
Once you have discovered a promising outcrop of lode gold the next step is to
sample the deposit. This can be done in
several different ways, but sometimes the old tried and true methods are the
best. The simplest way is to chisel a
channel right across the outcrop
of ore in which you are interested. This
is a lot of hard work but is well worth the effort. The chiseling is done with a one inch (25 mm)
stone chisel and a four pound hammer (2 kg), a short handled striking hammer works best for
this. The chips are saved in a cloth
sample bag for later assaying.
Another situation you may come across is several outcrops of
potential ore around your site
that is in this case too much to sample the outcrops singly in a first sampling
program on the site. In this case you
can go around the site and simply chip off a small sample from each outcrop,
then have it assayed. This isn’t the best
method for sampling channeling is, but at least it will give some idea of what
you have discovered. Be sure you keep
the samples random, and don’t favor what looks like hi-grade ore because this
will skew the results of your sampling.
If you want to be sure about the accuracy of your samples
send them to three different assayers then average the readings so you will
come up with an average reading instead of a single assay. This has been found to be more accurate.
After the preliminary sampling has been done, and your site
has been proved to hold gold it is time to go onto more sampling to find out
how much gold your site really holds, and if it is large enough to develop a
mine. It can take a lot of money to develop
a hard rock gold mine, sometimes more then a billion dollars. You should also keep in mind that only about
one in a hundred gold discoveries are eventually developed into a paying gold
mine. They call it lode gold because it
takes a load of money to develop it into a mine.
Drilling
the orebody is the accepted method of proving the size of a gold deposit that
is commercially viable. This is done
using a diamond core drill that gives you a solid core sample to examine. Core drilling rigs come in several sizes with
the smallest ones a drilling rig that can be back-packed. There are several companies that make these
drills that are capable of going at least 15 meters into solid rock. Even larger rigs are available capable of
drilling more then 1,200 feet into bedrock.
A back-pack
rig is within the scope of something a prospector can carry into the bush
with him, but larger rigs are best handled by specialized drilling companies. The samples these take are cylinders or stone
bearing the ore. The first thing that
happens when a core is retrieved is to split it in half lengthwise so the
prospector retains half of the core with the remainder being shipped off to an
assayer. A series of core drill cores are used to
delimit the actual size of an orebody by moving the drill rig further to the
initial hole until the last hole bored is beyond the last hole bearing payable ore. Many of these drilling programs encompass
drilling kilometers of core drill holes.
