The historic mines are positioned along an east-west trend of massive sulfide occurrences developed in and around a similarly oriented body of leptite
The basement comprises the Paleoproterozoic metamorphic rocks of the Wutai Group that is mainly made up of gneiss, amphibolite, leptite
, and mica quartz schist.
Generally speaking, the ore body in Zinkgruvan mine is hosted by leptites
. Further out in the hanging wall, there is limestone (marble) with considerably lower compressive strength when compared with that of the leptite
Like almost all other ore deposits in the Proterozoic of central Sweden, those of the Riddarhyttan ore district occur within a supracrustal rock sequence, including various felsic metavolcanic rocks and metasediments, known as the Leptite
we can see that for a 45-mm bit with spherical buttons, a force of approximately 200 kN is needed to press the drill bit 1.0 mm into the rock--in this case a Swedish leptite
. The rock resistance is therefore 200 kN/mm.