I use it because it is the simplest and least effort involved to get an estimate or comparison on a subjective topic.

Metal Mine Valuation ( just my compilation from internet, E.G. version 2012 )

Market determines stock price, we calculate value per share.

Estimate value of assets. (Metal in ground, infrastructures, cash on hand, etc.)
Apply percentage from below to above asset value.
Divide by number of shares outstanding. Result is value per share.

Determine stage of company: Land hold, Discovery, Exploration, Feasibility, Development or Production.
These determine average 'ball park' percentages of net value.

Initial Discovery: <1% ( Temporarily to 5%? on hype)
Exploration (NI 43-101): 5%
Feasibility: 10%
Development: 20%
Production: 40-50%
Purchase price: 60-90% of gross worth?
Gross worth: 100%

Discovery is finding of said metal whose quantity and quality is yet unknown but conjectured.
Exploration is drilling with documented reporting of findings.
Feasability is a study of economy of future mine.
Development is construction of mine ( infrastructure included) with associated costs arranged.
Economic Production is Gross Worth minus operating cost, environmental, royalties & taxes (bribery & politics), resulting in profits.
Purchase price is Gross minus expected profit (incentive to buy).