Underground channel sampling in geology may be generated and manipulated using various Channel Sampling methods. It is difficult to accurately determine the minimal channel width based on channel orientation, vein azimuth, and vein dip since channels are sampled from the vein at various angles.
How Does Channel Sampling Work?
To determine the minimum mining width, Channel Sampling employs a compositing process. Minimum mining width in actual vein depth is projected onto the channel plane to get the length of real vein length.
Using typical Vulcan compositing techniques, this length is then utilized to construct an ore composite, including any internal waste that may be necessary. Each channel gets the same treatment.
How To Choose A Sampling Method?
This question is raised early on in most placer investigations, but there is no straightforward response. Due to the fact that each deposit has its unique properties, there is no one “optimal” sample method or approach that can be used worldwide.
A competent pre-sampling reconnaissance will typically suggest if the ground should be examined using pits, shafts, churn drilling, or other ways. In certain circumstances, judgments will have to be taken sample-by-sample.
It is a contradiction that the very variables to be determined by sampling are frequently those that dictate the sort of sample to be collected initially. This is a “chicken-and-egg” situation in which we cannot always determine which came first.
Keep in mind that today’s placer sampling costs a lot of money. That’s why you should only employ methods or sample programs that give the level of depth and precision needed to make a particular judgment.
It would be pointless for a prospector whose primary goal is to attract the attention of another mining company to his prospect to spend his time and money on an extensive sample program, which any careful mining firm would perform over again for their own satisfaction and protection, as a result of the prospector’s lack of interest.
Often, the first placer sampling is only enough to suggest whether or not more exploration is necessary or to serve as a direction for future sampling or exploratory work.
Factors To Consider When Sampling
Several factors other than mineral composition influence the commercial value of placer deposits. Placer mining operations can be adversely affected by variables other than mineral value, such as hostile bedrock conditions, high sticky clay content, huge boulders, or other obvious hindrances to mining.
There is a requirement for experience in interpreting and making the proper judgments based on the information gathered from a successful sampling program. Limited information is obtained from placer samples. Rather than relying just on formulas, the engineer must rely on their ability to deduce and apply expertise to this knowledge.
Guidelines For Geological Sampling
Before beginning any placer sample, it is recommended that the site be thoroughly inspected. This may take an hour in smaller properties, but if the site is huge or has substantial mineral exposures, it may require several days of pre-sampling reconnaissance.
Obviously, the engineer must have some concept of the deposit’s size, shape, and general properties before developing an effective sample strategy. This preparatory study is critical. Unfortunately, many sample algorithms tend to skimp on this crucial first step.
Before doing any fieldwork, make sure you have copies of any existing aerial images of the subject area. Using images from the US Geological Survey or Forest Service is frequently the best reconnaissance tool. This is especially true when utilized in stereo pairs.
Additionally, good aerial images reveal topographic intricacies, drainage patterns, and other elements that would be difficult to perceive from the ground, giving the viewer a bird’s-eye view of the area.
This may be a huge time saver, especially in areas where the regional or local geology has been worked out by trained observers and described in authoritative publications. A review of published material should be part of any reconnaissance.
As a rule of thumb, it’s best to avoid relying too much on published material, especially for younger engineers who may not be able to assess the words and conclusions of others against their own experiences.
Placer sample selection and interpretation benefit significantly from the knowledge of a mining district’s history, which should be incorporated into the reconnaissance process.
Extra consideration should be given to any historic diggings in the areas to be sampled, especially if any product has been made from them before. New samples can be selected and interpreted with the help of production records if they are available. Whenever feasible, it’s a good idea to visit and inspect any nearby mines.