Rooster Rock Geological History

The rock here is the Rhyolite of Hash Rock, a volcanic formation about 39 million years old.

This Eocene rhyolite is part of the volcanic system associated with the ancient Wildcat Mountain caldera. The northern part of the Rhyolite of Hash Rock extends from the caldera toward Rooster Rock.

Freshly broken rock may show flow banding—thin, wavy layers formed as the lava cooled. These layers are still visible millions of years later.

As the rhyolite cooled, it developed cavities and fractures. Later, silica-rich fluids moved through the rock and deposited minerals in these openings. This process formed agate, quartz, and thundereggs.

Rooster Rock Rockhounding

Agate is the main find here. Common types include clear, gray-banded, blue, and moss agate. Some pieces have cavities lined with quartz crystals.

Red jasper can also be found, although it is less common.

Thundereggs are another possibility.

You can find loose pieces on the ground and along road cuts. Agate can also occur in seams within the rhyolite.

Start by looking at the surface. Tumbler-size pieces can be found on the slopes and near the road. I found my first pieces within five minutes of parking.

Take some time to examine what you find. Not every piece of rock is worth carrying home. After you find a few good specimens, it becomes easier to recognize better material.

If you are looking for a larger specimen, look for outcrops where agate seams are visible in the rock. Some seams contain blue-banded agate.

Removing material from an outcrop takes care. A hammer and gad can be useful. Work slowly along the seam rather than hitting the rock hard.

🟡 A few things to know before you go: You may see agate in the gravel road, but do not dig into the roadbed. The road needs to remain passable for other visitors. Also watch for mining-claim markers and stay off active claims unless you have permission to collect. Wear sturdy boots with good ankle support. The slopes can be steep and loose.

Whistler Campground is a free, first-come, first-served campground about 5 miles up the road. Check the area above your campsite before setting up. Standing dead trees can fall and may be a safety hazard.

Dispersed camping is also available in the surrounding national forest. We have found good places to camp along NF 2730.

If you prefer a hotel, Prineville has several options, including hotels and vacation rentals.

Affordable vacation rentals for short and long term stay at Prineville

Lodging in Prineville

Open: June through October (snow can block roads until May)
Managed by: U.S. Forest Service - Ochoco National Forest

Rocks & Minerals: Moss agate, clear, blue, gray agate, quartz crystal nodules, red jasper, thundereggs
Tools: Geology pick, rock hammer, gad, chisel, shovel

Distance from the parking: Varies
Road access: 4WD vehicle is recommended
Fees: None

Elevation: 5,100-5,300 ft (1,555-1,615 m)