Just about all retail shareholders of a taken over company feel being robbed.
In-ground assets are always devalued severaly in valuation.
I know in gold and silver stocks ( I am mostly a PM bug) if you do not have your drilling complete (i.e. still an explorer at an early stage ) the devaluation is down to below 5%.
Establish a resource with a 43-101 and you are at about 5%. Produce a feasability study and you may reach 10%. Get a mine permit with some basic infrustructure ( such as road access ) and arrange financing and it approaches 20%.
Near production, 40%.
These apply with no unusual complications in place, derate further if so.
Almost never over 50% because royalties, taxes, financing costs after operating expenses produce a cap. I do not see any reason for things to be much different with other metals.

So to cry 'We are undervalued' is just belly aching, especially in this market.
Of course you are, that is the nature of the beast.

A major will come in once there is a sizable resource established to make their investment effort worth while. Not only a resource but it almost always has to be near production. They are not interested in doing the exploration, their interest is in production to maintain market share.