Channel Sampling for Minerals
Channel sampling in rock can be a difficult chore depending upon the hardness of the rock. This technique is generally used when sampling underground openings (drifts, tunnels, adits, cross cuts) and trenches dug in rock. The best approach is to chip a sample of rock that is one half to one inch deep and six inches wide for the full length of the wall being sampled. The rock that is chipped off the wall should be collected as it is removed and stored in sample bags which represent a regular sample interval if the rock type is homogeneous. If there are changes in the rock type then the sample interval should correspond to the changing rock types.
If the rock is too hard to obtain a full width sample it may be advisable to make a narrower, sinusoidal channel from which to take the sample. Taking channel samples is a tedious process but the samples are very good representations of the rock of interest and care must be exercised to ensure that the samples are correctly taken.
The tools required for channel sampling include a large chisel with a hardened point and a hand mallet to hammer on the chisel. Safety precautions must include durable gloves and full coverage eye protection for both the person chipping the sample and the one who is collecting it as it is removed.
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