- In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between 56 and 47.8 Ma, is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian is consistent with the lower Eocene.
- 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.