The Baltic Mine, 3rd largest producer in the Keweenaw native copper district opened about 1898 and was worked for ~60 years. This amygdaloid mine is a flow top breccia which dips about 70 degree NW and was 5-8 m thick. It was mined for about 7km along strike. The minerals found here associated with copper include quartz, pumpellyite, epidote and calcite. Chalcocite, bornite, siderite, laumontite, prehnite, barite and chacopyrite are also found. Baltic Lode details.
Baltic Shaft #2 1897
This site allows us to see amygdaloidal rocks which show permeable pahoehoe and aa flow tops where voids were filled with minerals by hydrothermal fluids during burial of the flows by younger lavas and subsidence of the rift valley. The minerals formed over a period of 30 Ma, after the flows formed.
