546662 mE 4934572 mN 382 m (UTM10N NAD83) (Google Maps)
548847 mE 4935318 mN 582 m (UTM10N NAD83) (Google Maps)

Bureau of Land Management

The Quartzville District pyrite localities are apparently well known to Oregon rockhounds, but despite the fame and popularity one can still find very nice specimens in this area. I stopped by two separate locations when I visited the locality. The first is near the confluence of Yellowstone Creek with Quartzville Creek. At this location, tourmaline (var. shorl) and chalcopyrite/pyrite are found in altered volcanic rock. Small, black, radiating masses of tourmaline are found within a white, powdery alteration rock. Clusters of tourmaline can also be found with chalcopyrite and pyrite in crumbly oxidized rock.

The second location is the famous Boulder Creek pyritohedron locality. Here, pseudo-dodecahedral pyrite crystals (pyritohedrons) are found within an alteration zone. The pyrite crystals are up to a centimeter across. They are generally only half of a full pyritohedron, however, so they look better left in the clayey matrix. The pyrite is generally silvery in color, but bronze-colored crystals are also present. The alteration zone at the Boulder Creek occurrence is very interesting. The country rock has been completely altered to a clay matrix, within which the pyritohedrons are found. The alteration zone continues across the road, down to Boulder Creek, but it appears to become more of a breccia zone that lacks pyrite once it crosses the road.

A Geological Field Trip Guide from Sweet Home, Oregon, to the Quartzville Mining District (Oregon Department of Geology & Mineral Industries: The Ore Bin, vol. 39, no. 6)

Gem Trails of Oregon, Garret Romaine