Fossils, Rocks & Minerals - Oregon

Nationally known as a great place for rock hounds, Oregon produces a great variety of types rocks and quartz minerals. The plentiful mineral deposits of the state are supplying the museums, private collections, and shops with colorful and valuable semi-precious gem and cut rock specimens.

Oregon Fossils, Rocks & Minerals

Agate is a translucent or semitransparent a fine-grained cryptocrystalline quartz composed of silicon dioxide SiO2. The tough and attractive mineral has excellent working properties. Read more...

Fossilized Agate - an agatized form of marine life such as clams or snails. Engulfed by lava, all inside of the shell has been replaced with agate and other types of chalcedony.

Jasper is like agate originated from chalcedony (a type of quartz) and features iron oxides, hydroxides and other impurities that create unique color combinations. Read More...

Geode is a hollow rock, often with mineral growth inside. Mostly, filling-materials are quartz crystal but may include opal or zeolite.

Thunderegg is the round nodule-like rock formation, filled with agate, jasper, opal and other minerals. Read more...

Limb Casts or Fossil Wood formed in volcanic ash cavities which before were occupied by wood. The wood structure is either burned out or decayed. Later, minerals from groundwater have been deposited in the cavities.

Limb casts are found in Central Oregon - the Congleton Hollow and Dendrite Butte sites.

Obsidian - a volcanic glass that is classified as an extrusive igneous rock (not a mineral). When basalt cools quickly by contacting with water, mineral crystallization is minimal. Basalt forms into a glassy structure. Obsidians are brittle and mostly black with green, purple, bluish shades viewed on the fractured shiny surface.
The best place to find a variety of iridescent obsidians is the Glass Butte Obsidian in Lake County of Southeastern Oregon.

Opal - a hydrous amorphous (non-crystalline structure) form of silica. Common opal is widely-distributed in Oregon and Nevada. Precious fire opal is rare. In Oregon, the opal deposit has been found in Morrow County, Opal Butte. However, this location is not available to the public.

Opal collecting for fees is available in Northern Nevada: Royal Peacock Opal Mine and Kokopelli Opals Mine.

Petrified wood, also known as Fossilized Wood, is fossilized remains of ancient tree plants from the Paleocene Era. The name "Petrified" came from Greek "petro" that means "stone", literally, "wood turns to stone". Read more...

Sunstone is a transparent or translucent feldspar crystal with a wide variety of colors including clear white, yellow, red, green, and blue. The size of specimens is usually between an inch and two. Read more...

1. Arthur Thomas. "Gemstones: Properties, Identification and Use". 2008.

2. "Oregon Rocks, Fossils Minerals". Josefine County. Oregon Historical Society.

3. Nancy Marie Brown. "How Do Agates Form?". 2001. Penn State University.

4. Dr. H.C.Dake. " The Gem Minerals of Oregon". 1938. Portland, Oregon. Oregon State Department of Geology and Mineral Industries.


  1. I am interested in collecting ores in Oregon for hobby smelting. My preference is for copper ores since the smelting process for copper is relatively easy. Secondarily, I am interested in iron ores (the information you provided concerning rhodonite was very helpful).

    Thank you for the excellent article on rockhounding in Oregon!

    1. I don’t know of any place in Oregon that has copper deposits in mine-able amounts.

      The best states are Arizona, Utah, New Mexico, Nevada and Montana. There is also a little in Idaho.

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