Situated some distance west of the Washington Mine proper is a short adit driven into the hill to crosscut a thin deposit. Although it is possible this operation was undertaken by the Washington Mining Company, this has not been confirmed. Evidently, this was nothing more than a small prospect to attempt to mine lead and zinc ore from a lower elevation. No stoping was ever undertaken and subsequently, no ore was ever shipped.

The Washington Mine was first operated in 1863 and it is likely that exploratory work was conducted here around the same time. When the Erie Railroad re-routed its mainline in the early 1900's, the right of way passed within 20 feet of the entrance. Today, passenger trains regularly pass this obscure mine adit while traveling through the Shawangunks.