Ann: 27m Grading 66.8g/t Gold, Bulago, PNG , page-22

XRF handheld measure about 1cm2 and you need more than 20 reading from various parts of the rock to get an "average". Even then they are high risks, particularly where the mineralisation is lumpy and bias can occur. I have written many ASX announcements and would not include XRF results. They are handy when you are in isolated areas and it will take months before you get the results. Companies use XRF for soil lines in Botswana where the instant results permit you to change the programme focus.

Float samples are indicators of what is the area. The risk is that you may never find the source I found a float sample in PNG that went 0.1% gold and 0.2% silver, however despite a thorough search I never found the outcrop.

Grab samples are supposed to be a random and a general indicator of the grade from a dump or vein. However there is usually some bias towards what looks higher grade and these should be called a selective grab. A true grab sample can be taken from a tailings dump where it is usually difficult to bias the sample.

Rock samples are usually good and indicative of the mineralisation. It does depend how you taken them. Using a G-pick or chisel may be good if the outcrop permits. In many places they prefer a portable diamond saw as it gets a better sample.

"The outcrop continuous chip samples were collected where possible by their exposure and orientation and do not necessarily represent true widths of mineralisation."

It is not possible to determine whether the vein is larger or smaller from the announcement. If the mineralisation ends in an area where there is no outcrop then it may extend further. Then again quartz veins may be erosion resistant and hence it the reason for the outcrop. Where the mineralisation outcrop ends is where the mineralisation actually ends.

The key feature is the dip of the mineralisation compared to the slope of the ground. The slope of the ground is to the south (given by the direction of the Y shape of the creeks). If the mineralisation is dipping to the south then the true width may be reduced considerably. If dipping to the north then the apparent width may approach the true width.

You should be able to determine the mineralisation dip by the direction of the mineralisation outcrop V in the map where it cuts the creek however the mapping in the announcement is schematic rather than accurate and hence it is not possible.

Drilling is usually a better sample but I have seen some core with huge core losses in the mineralised zone making them all but useless. It also depends of the core diameter and the size of the gold grains. Rock samples can be better than core as you can take 10s kilograms of sample Vs perhaps 1kg from split core.

As with any sampling, it depends on the equipment, the sampling crew and geo.

See also my previous post.


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