Hello Jon,

yes "exploratory" is the right word, I think.

The rest., ... no not "claim".

Mining is a very old business in Germany, when the Rammelsberg

was closed in 198x, this mining was more than 1000 years old.

And: often special words in old professions retain the meaning

of the word centurys ago.

Mutung is related to Mut, Gemüt, Vermutung, and English mood !

The closest modern use is "Vermutung" (assumption). 

Where You assume that something is to be mined, You make

a "Mutung", which means to dig (today maybe a drill) some

dozen/hundred  meters down to look for "Höffigkeit"(wether there is some

promise.

The word is used by miners only, average Germans would not know it.

Georg