Strange but beautiful.

Asked August 21, 2019, 6:51 PM EDT

Hi my name is Blue Harrington, a friend of mine gave me these two rocks just was wondering what they might be. They are large and heavy the first picture is one. The next two are front and back of the other.

Wasco County Oregon

1 Response

Hi, Blue - I'm making an assumption that your friend picked these up somewhere in Wasco County which is part of the Columbia Plateau physiographic province. Even though the area is underlain predominantly by Columbia River Basalts, there are some rhyolitic volcanic mudflows (tuff) (lahars) west of Dufur. I suspect the first rock is a tuff. The second rock appears to be basalt, exhibiting some fun rope-like drip features. Next time you are at the junction of Hwy 197 and I-84 at the Dalles, look at the road cut on the east side of the highway. The rock is called "pillow palagonite" which describes the process it was formed by. A molten basalt flow rolled into a water body (lake or river) and quickly chilled the lava, rolling it around into big blobs (pillows). Sometimes the lava chills in strange shapes. I like the water feature in the first rock! For further information, check out the Oregon Department of Geology and Minerals Industry website. Nice rocks!