I would probably put more faith on the on ground geologists than a random HC poster as they probably have an inkling on what they are looking on the ground. Nonetheless, having a guess:
1. 10 to 15 holes for 1500 metres too me is based on getting as much information on the potential deposit as possible. I suspect that each hole will be about 100 to 200 metres apart so with that can test a large area (i.e. known in JORC as testing an inferred resource only).
2. The depth of each hole looks like it will be 100 metres (if 15 holes are drilled) or 150 metres (if 10 holes are drilled). I suspect they think they have a 'shallow deposit" that might go beyond depth (meaning the hypothesis they are working with is the graphite ore body they think will be intersected before 100 metres and if so and it goes beyond the depth of the drill bit they will just be happy, assuming grade and width of graphite intersected is good). Be mindful, from a theoretical perspective you want to be intersecting the ore body between 40 metres to 100 metres (if closer to the surface even better) because that increases the likelihood of a prospective mineable orebody as don't want to be moving too much overburden. That is the deeper the ore body before intersection it will need to have greater width and grade to make it viable given overburden removal etc.
3. Why Diamond Drill - this stumped me as well in the 'quarterely but suspect it could be for three reasons:
i.) if you think about RC drilling the core is broken up significantly coming out like shredded/fragmented rocks. A Diamond Core is essentially an intact cylinder, meaning the core gives your geologists/computer modelling programs additional information/data around the actual makeup of the ore body and what they will need to deal with in mining. It is actually more precise including seeing the rock structure and viens within it. When you do a few DD you can actually then map angles and layering of the deposit structure more than a RC core. In terms of assaying it probably gives you much better information around metallurgy as well since in bringing up your core in DD or RC you generally are also pumping water down the drill bit so can 'wash away' some of the contents of a RC (and other drill types), but not a core because it is intact.
2. What I am saying is you have far more confidence with DD assay results than RC ones, and ultimately you still need to do DD at some point.
3. But why now and not later is the question - either i.) they are confident of what they have, ii.) they are using DD now which actually helps to claw back some of the lost time in not doing the drilling earlier because ultimately you do need to do some DD noting iii.) they are not going that deep with a DD compared to a RC. Alternatively, they could be using a DD because of the rock types they are encountering meaning RC might not be as effective in the area than DD (the stability platform for drilling and potential issue of 'refusal') but I don't think that would be the reason given RC is used in icy plains/cold environments etc.
Just a guess, but yes DD is more expensive than RC. For those going to the AGM would be an interesting question to pose to them that you are raising btw.
All IMO