Summary of MMS article - 

I found these portions of the article to be of particular interest.

NOT has these 'pertubations' from our mother hole #5 and is able to thus assess other anomolies.
"Anomalies", or unexpected perturbations in these fields, are recorded and compared with responses theoretically expected from sulphide bodies.

Basics:
An "assay" is simply a chemical analysis that determines the amounts of easily extractable metals in the sample; assays of the base metals (e.g. Ni, Cu. Zn, Pb, Co) are usually expressed in weight percent; assays of precious metals (e.g. Au, Ag) are usually expressed in grams of metal per tonne of rock

What can the drillers see?
The question of 'visible' mineralization in the drill core:
The nature and intensity of any mineralization is clearly visible in the drill core and when mineralization is encountered, a portion of the core is sent out for assay.

Are we rich YET (adjust $ amounts)? 
Calculation the amount of Nickel (note - pricing used is obsolete):
Consider an intersection over some significant width reported to grade 2% Ni and 1% Cu. The amount of Ni present in a ton of this rock is easily calculated. One tonne contains 1000 kilograms (kg) and at 2% Ni, would contain 1000 x.02 =20 kg of Ni. Similarly, it contains 1000 x .01 = 10 kg of Cu. 1996 Ni and Cu prices were about $3.85/lb. and $1.30/lb., respectively ($US) (we use non-metric price unit measures because metal prices are typically quoted in $US/lb), so the value of a tonne of rock at these grades is (20*$3.85*2.204) + (10*$1.30*2.204) = approximately $200.

And the summation of summations - What to consider while you do your own DD:
A few brief rules of thumb for evaluating the significance of new massive sulphide discovery might be as follows:

massive sulphide deposits are small, difficult to find targets. For every large, high grade deposit, there are likely to be large numbers of small, lower grade deposits. Massive sulphides generally have higher grades than disseminated sulphides;

Airborne geophysical anomalies may indicate the presence of sulphides and are excellent targets for further exploration; but they may also result from other geological features; grab samples with interesting assays clearly indicate the presence of mineralization on the ground, but provide little indication of the potential size or overall grade of the occurrence; channel samples provide a good systematic sampling of mineralization at outcrop scale and an indication of the width of the mineralization as well diamond drill holes normally provide the first three-dimensional picture of an occurrence. assays of drill core provide vital grade and width information, both of which must be considered in evaluating the significance of a result. Grades provide good information on the relative value of the mineralized zone but are not necessarily the grades that will eventually be mined; estimates of the value of an orebody must include some estimate of the metal prices in the future.

And from the VMS article -

 VMS deposits tend to occur in districts. Up to two dozen deposits, might be clustered in an area of a few tens, of square kilometres. Known VMS districts are good hunting grounds for new discoveries.

Deposits within a specific district tend to have similar metal ratios and a fairly narrow range in composition. In any given district, deposits will tend to range in size from less than one million tonnes to several tens of millions of tonnes, with most deposits at the small end of the range and only a few large deposits.