Note: I've added dashed lines to the charts where data is missing (the Dec 2016 resource press release didn't include information for M&I and inferred resources).
We can see that that we had an initial increase in resources from 2011 to 2013 and then a leveling off as drilling focused on improving resource quality and converting resources to reserves. We see that recently drilling has also focused on increasing resources.
Ounces have stayed relatively flt over time, we had very large growth in resources from 2011 to mid-2012, then the focus has been on improving the quality of the resources (from Inferred to Measured and indicated) and to reserves in 2016.
I've added a lines for the Life of mine (LOM) mine grades in the 2014 Feasibility Study (FS - orange line) and the new 2019 proposed mine grade (purple line), and one for the 2018 actual mine head grade (grey dashed line).
- Average grade (all resources) decreased from 22 g/t Au (2012) to 15.8 g/t Au (2019)
- M&I resources remained constant since 2012 at ~17.1 g/t Au
- Inferred resources decreased from 35 g/t Au (2012) to 17.7 g/t Au (2019)
- Reserve grade decreased from 16.1 g/t Au to 13.8 g/t Au
Obviously the reserve and resource grades have dropped because of all the high-grade mineralization mined in 2018......
You will see that in many 43-101 reports the Inferred resources typically higher grade than the other resource categories, they are normally based on the lowest quality data (relatively speaking), the widest spaced drill-holes and can be heavily skewed by a few ultra high-grade holes. However, it is surprising that the grade of the inferred resources have fallen by such a large amount.
This figure was also interesting in the press release:
There was a lot of technical crap in the section accompanying this table, but in I think it means they mined 20% more material than planned, now this will be interesting to see going forward, especially with the mine being expanded to 3800 tonnes per day.
Brucejack produces a lot of gold, but it keeps falling short.
Data for these charts came from:
Feb 2011 resources - link
Nov 2011 resources - link
Apr 2012 resources - link
Sept 2012 resources - link
Nov 2012 resources - link
Dec 2013 resources - link
July 2016 resources - link
Dec 2016 reserves - link
Apr 2019 reserves and resources - link