I'll have a stab at it it in terms of "reserve" explanation. Bear with me its a rainy day, our share price is bleeding. and I have spare time to tell a story in my own words. You could also skip to the last link on the bottom for someone who is probably right on to what youre chasing.
Old mate geo goes walking around in the bush kicks a rock over - BAM! there are minerals of value in it. Looks like this is a deposit based on surface based geological observations of the land and possibly remote sensing techniques on the desk top of varying degree. (Probably why he was out there kicking rocks around in the first place)
Spend some money test the rock and its formation on surface along its strike line or outcrop, comes back viable for mining in terms of metallurgy to get the minerals out and of a reasonable high grade for whatever mineral. Also very importantly there is a viable/reasonable way to get the material to a market for this material logistically (ie its not in Antarctica or the top of mt everest etc)
Drill. Drilling is next, and inevitably should continue in staged process - of course with geological direction! Drilling as we all know is rather pricey. The drilling process is the only thing to determine a deposit's reserve potential. It costs money but you don't know until you go - nor can you convince investment in a geologically mathematical statistically based way (this is generally what the JORC code represents)
A "grid" of holes are planned over the resource based not just on the size of the resource but also how much money you initially have to spend on it. Usually the grid spacing is quite large to define the potential size of the resources, and when you're lucky and this next stage also is a success. As the success of ore definition increases the grid spacing becomes smaller to define it to a probability point that meets the JORC code parameters.
Geology is not exact. Even after investment and mining right through the project - continued drilling is required to ensure grade control. For example in pit mining which is far simpler to explain a grid of holes in stages closely spaced is drilled to define the ore versus waste as each flitch (level) of the pit floor is mined.
But back to the code: Reserve definition according to JORC isn't based on economics as much as the geological probability that your model created with the facts gleaned from drilling is as close to reality as possible. that is Reserve definition in a nutshell.
The price of the material will wax and wane - but the reserve is a size or quantity of material defined geologically, will grow or reduce as factual information is gleaned from drilling and mining - and of course reduced as it is mined. Changing the cutoff grade will change the economic viability of each mineable "block" of the resource usually mapped in finite element modelling of the resource information including assay of mineral being mined. Is the overall block model of ore and waste taking into account just the cost of mining? or also the corporate name change costs for example?
Here's where it gets curly, as we now bend economics into the science... And so I leave you to this info which hopefully explains in economic terms you're looking for Names.
