- Denny Mountain (mindat.org)
Denny Mountain is one of the better known mineral collecting localities in Washington state, containing a wide variety of attractive skarn minerals. It is the site of the original Denny Claims which followed the contact mineralization. Originally located by Artur Denny (one of the founders of Seattle) in 1869, it was the first recorded lode in the Snoqualmie Pass area. Most of the early work there was in search of economic quantities of Iron. The grade found was fairly high in places, but the impurities in the magnetite and hematite made it useless. Some chalcopyrite was also found but the quantity was insignificant for mining.
- Extrusive rock (Wikipedia)
Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In contrast, intrusive rock refers to rocks formed by magma which cools below the surface.