Antler Project Discussion, page-7

Downhole-width v True-width v Horizontal-width

In the JOC notes NWC state they have reported downhole intersections for historical holes. Previous Resource estimates reported "true-widths" and "horizontal-widths" with the actual DH intersections in appendices not available on the net. In the 1975 PFS report by Gilmour, he discusses the issue of "true-width" interpretation and some discrepancies between his interp and previous studies. He rightly observes that relatively slight differences in the dip of the hole and mineralisation will impact the estimated intercept angle and thus the 'true-width' of an intersection. That a small change in dip assumptions of either the hole or ore horizon is worth keeping in mind imo.


So 4.9 ft (1.49m) is the Gilmour's 'true-width' interp, which translates to 5.9ft (1.8m) 'horizontal-width' meaning the assumption was made the orebody was dipping just below 60deg to the west. NWC reported B-4 as 1.65m 'downhole-width' (5.4ft), which is 10% above true width (at the same grades so we know it's exactly the same 4.9ft intersection ).


This is only one hole but it proves NWC reported historical downhole intercepts are downhole only as stated, and that 'true-width' depends on logs/data they may not have. A quick check of some hole data presented in the report confirms to me that 'true-widths' might be fairly close to 80% in general of reported DH intersections.... similar to what they said in the Jan release. Obviously my review is woefully short of data to be anything more than a thumb suck, but it serves to give me some confidence in how to use the old results.

Horizontal-widths are important, because if we are going to look at a dipping plane projected to vertical, true width will under estimate the quantity of ore. Imagine standing in an u/g ore drive looking at the ore face dipping steeply west in front of you. true-width is not horizontal with the floor or perpendicular to vertical as for our LS. Any polygon resource estimation in the vertical plane needs to multiply 'horizontal-width' by the LS vertical height to arrive at a correct estimate. This actually is a positive upgrade to what some people might have been using to do their own estimates of how big the resource is, though probably it just cancels out an error.

In short, the historical DH-widths reported on the NWC LS are exaggerated by roughly 15-20% on average say. Horizontal-widths are roughly 15-20% wider than True-widths for an orebody nominally dipping 60deg or a bit less to the west. Therefore, we simply ignore the true-width issue (in general but obviously every hole is different) and multiply the LS vertical height by the DH-widths (then by strike) to arrive at a rough volume for any LS polygon.

The same could might be true for recent NWC drilling, but not for holes that go from 80% to 60% true-width obviously. At that sort of 'downdip' exaggeration and further adjustment to ore widths need to be made. As per my very first post on NWC, it's only the later deep holes drilled from the NW that look to be moving further away from 80-90% true width exaggeration by necessity. Hitting the very small target is the priority from these pass, not trying to hit the target square... Unfortunately we haven;t been given any info on what results are more or less away from true width, just that it is happening from these new pads.

Apologies I this is becoming a bit technical and dry, understand completely if it's not your thing.