Oregon Rocks and Minerals

Oregon is home to some of the most pristine geologic regions. From the coast to the Cascades, Crater Lake, and the Columbia river expanding through rolling hills, Oregon’s geographic history is rich.

Off the coast of Oregon, an oceanic plate collides with the western coast of the United States, creating a subduction zone. This subduction zone slides deep beneath the edge of the state’s continental shelf and is drawn deep into the Earth, where it causes rock to melt. This process feeds a chain of volcanoes called a volcanic arc, which is known today as the Cascade Mountain Range.

Inland from the volcanic arc, a rift zone may open, tearing apart the continent along dozens of faults. The processes of plate tectonics, particularly subduction, have shaped Oregon throughout its entire geologic history and have continued to shape the state today.

Also contributing to some of the rock formations in the northern part of Oregon, was a massive flood that occurred over 10,000 years ago. The Great Missoula Flood is a historic geological phenomenon that was a result of melting glaciers.   

The flood spread across regions of Idaho, Washington, and Oregon. Some deposits of The Great Missoula Flood can be found in the Willamette Valley. These deposits of erratic rocks are large boulders that have been deposited by these melting glaciers. What makes these boulders unusual is that they have traveled hundreds of miles due to the powerful force of the floodwaters. Oregon has an Erratic Rock State Natural Sight in McMinnville, just 50 minutes south of Portland. 

Close to the Oregon-California border in Ashland, OR there is another geologic phenomenon that occurs. A spring, abundant with deposits of lithium, lies in the center of town and has been transformed into a lithia water fountain. This attraction has brought many visitors to the area to try this fizzy, smelly, and bad-tasting water. It is hard to drink more than just the smallest amount possible due to the bad taste. But the lithia water is special due to the fact that it can create positive chemical responses in the brain that can help people avoid feeling sad. 

In La Grande, geothermal hot springs are an attraction for many people. These hot springs are caused by circulation through faults to hot rock deep in the earth’s crust. Mineral deposits within the water produce healing properties for treating certain skin irritation. 

Oregon is also one of the best states in the United States for finding rocks and minerals. Since Oregon has a high percentage of public land, many people from all over the world visit Oregon to rockhound. Rockhounding is a common term used to describe amateur geologists or rock collectors. Facebook groups have become a new way for rockhounds to share information about different rockhounding sites, and also show off their rock collections. The best thing about searching for rocks and minerals is that it’s usually free! 

Agate, jasper, geodes, thundereggs, obsidian, opal, petrified wood, and sunstones are just some of the rocks and minerals found in the state of Oregon. Getting started only requires materials necessary for the job. A bag to collect the rocks is a good starting point, other equipment may include a rock hammer, rock chisel, brushes, safety goggles, and some gardening gloves. 

Oregon’s state mineral, the sunstone, is a feldspar crystal that has weathered out of certain lava flows ranging between southern and central Oregon. An Oregon sunstone gets its name from its yellow-amber-like colors, in which the transparency of the colors depends on the amount of copper deposited in the stone. Scattered across the driest terrains and situated north of the Nevada-California-Oregon stateline lies Plush, Oregon, a great spot to find Sun Stones that lie on the surface of Oregon’s most remote areas. 

Just southwest of the Grande Ronde Valley, minerals can be found from an ancient rhyolitic volcano called Tower Mountain Caldera. A Caldera is a hole that results from a collapsed volcano. Geodes, opals, and thundereggs are also found in the rhyolite near the Tower Mountain Caldera, west of Sheep Creek, and along U.S. Forest Service Road 5160. 

Rockhounding can be a good hobby to pick up because of its reward, it is also lots of fun! Serious rockhounds will sometimes invest in a rock tumbler/polisher, or even a rock saw, allowing them to display all of the beautifully intricate designs of their rocks. 

If you want to go visit one of the best rock museums in Oregon, visit the Rice Northwest Museum of Rocks & Minerals located in Washington County. The Rice Museum showcases world-class rocks, minerals, fossils, meteorites, and gemstones. The Museum is also listed on the National Register of Historic Places.

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