Todays PR... I had a look at the BGM press release. as press releases go, it is not bad in that there are a lot of cautionary statements below the table which are bang on, if anyone reads them... a few things:
I am a little confused by the difference between "mean grade" and "mean length weighted grade"... normally what that would indicate is that, for the data set as a whole, the mean in the first case would just be an average of all the values in the data set. for the second case, they would multiply the assay value x the length of the interval, add it up and divide by the total length, thus giving more weight to the longer intervals. you can see how the mean drops significantly in the second case, indicating that, for the data set as a whole, the longer intervals tend to be lower grade than the higher grade intervals. that is normal in skinny vein deposits, as the vein intervals might only be a foot long, and dead rock is general sampled at some pre-set length like 5 or 10 feet. The mean/median values, and the per cent change in values, is more meaningful for the length weighted set because it gives a better picture of the overall distribution of nuggety high grade in the data set analyzed. so far so good. but... the "Min" and "Max" values should be IDENTICAL in both cases, because it's the same data set in both cases, and they are not. this is a big red flag IMO.
Note that the MEDIAN value, the value for which there is an equal number of samples above and below that value, is well below cut-off, basically dead rock. this suggests that they are not adding much, if anything, by assaying the rock outside of the veins IMO.
The Std. Dev. and CVs are off the charts high! Normally, for a resource calc., you would want the CV to be below 2, and the way you get it is by compositing the assay intervals into longer intervals, and if the CVs are still high, by capping either the composited or raw assays. Higher CVs (but not that high!) are warranted if the geological controls are very well constrained, but I don't think this is the case here IMO.
No way to tell how the analyzed drill holes are distributed in space, but it would be tempting to say from this that the "average" grade of the rock is the mean of the length weighted data set, and if you mined it all, that's what you would get. that is NOT the case at all!!! the median is telling you that MOST of the rock is dead! you can get the same average grade by taking that 955 gram "max" sample, assuming it is 1 foot long and smearing it over 900 feet of dead rock!
anyway, that's what I see... Anyone looking at this should do their own interp., and this are just a few of the things I took from this. In no way is it ment to be a bash, it is just my comments with regards as to what was released.