Idaho Highway 3 Roadcut – April 2022

Idaho Highway 3 Roadcut

This roadcut on Highway 3 in northwest Idaho is mentioned in a few sources as having opal in the basalt and even opalized wood. The primary mention of this location is in a masters thesis from the mid 1990s.

Minerals listed as occurring in this location are pyrolusite, red opal, white opal and wood opal. We found only pyrolusite and no opal. The pyrolusite is a small, black dendritic pattern on the basalt. While interesting, this is probably not enough reason to go out of your way to check out this roadcut.

This is a great roadcut in terms of the abundance of shoulder on the sides of the road and plenty of places to safely pull over and park. The road wasn’t too busy when we were here on a weekday afternoon.

The basalt has many good examples of pillowing as well as polaganite. Another roadcut leading up to this one had some very nice sinclined basalt columns.

When we visited, the snow had completely melted but in the winter snow from plowing would make this roadcut inaccessible. This is probably not a destination but if one is driving down highway 3 in Idaho and wants to stop and admire some basalt, this would be a good place to go.