🦴 Fossils For All

Fossil Hunting in Colorado

intermediate friendly AmmonitesBaculitesFossil insects (Florissant)Petrified woodBivalvesDinosaur bone fragments

Colorado is one of the most paleontologically significant states in the country. Its geological diversity spans from Precambrian basement rock to Tertiary volcanic deposits, and its fossil record includes world-famous dinosaur quarries, exceptional Cretaceous marine beds, and the unparalleled Eocene insect locality at Florissant.

Why Colorado?

Colorado’s position along the Front Range of the Rocky Mountains places it at a geological boundary where ancient marine sediments from the Western Interior Seaway abut against uplifted Precambrian and Paleozoic mountain core rocks. The Cretaceous Pierre Shale, deposited in the shallow seaway that once split North America in two, is exposed along the eastern plains and foothills. The Jurassic Morrison Formation, source of some of the most famous dinosaur discoveries in history, crops out along the hogbacks of the Front Range.

The state also boasts vast tracts of BLM land where responsible fossil collecting is permitted, making it one of the more accessible western states for hobbyists.

What You’ll Find

Jurassic fossils (Morrison Formation, ~150 million years old):

  • Dinosaur bone fragments — Surface fragments on BLM land (vertebrate excavation requires a permit)
  • Gastropods and bivalves — Freshwater invertebrates from Morrison floodplain deposits
  • Petrified wood — Conifer wood from Jurassic forests

Cretaceous marine fossils (Pierre Shale, ~70-80 million years old):

  • Baculites — Straight-shelled ammonites, extremely common and sometimes iridescent (ammolite)
  • Ammonites — Coiled forms including Placenticeras with occasional iridescent shell
  • Inoceramus — Large flat bivalve shells characteristic of the Pierre Shale
  • Shark teeth — Squalicorax and other Cretaceous sharks
  • Mosasaur fragments — Rare, and vertebrate material requires a permit on federal land

Eocene fossils (Florissant Formation, ~34 million years old):

  • Insects — Extraordinarily detailed preservation of beetles, butterflies, ants, and wasps
  • Leaves — Sequoia, Fagopsis, and many other plant genera
  • Petrified redwood stumps — Massive silicified tree bases (visible at the monument, not for collecting)

Best Time to Visit

  • Late spring (May-June): Snowmelt recedes at lower elevations; pleasant temperatures
  • Summer (July-August): Best access to higher-elevation sites like Florissant and Kremmling, though afternoon thunderstorms are common
  • Early fall (September): Excellent conditions with low humidity, warm days, and cool nights

Tips for Colorado Collecting

  1. Know the rules on federal land — Invertebrate and plant fossils can be collected in reasonable quantities on BLM land for personal use, but vertebrate fossils require a research permit
  2. Check concretions in Pierre Shale — Ammonites and baculites are often preserved inside harder concretions that weather out of the soft shale
  3. Visit Florissant Fossil Beds National Monument — Even though you cannot collect there, the visitor center and trails provide essential context for the region’s paleontology
  4. Bring layers — Colorado mountain weather changes rapidly; even summer days can turn cold at elevation
  5. Join the Western Interior Paleontological Society — WIPS runs excellent field trips to productive Colorado collecting sites and is one of the most active fossil clubs in the western United States

Collecting Sites

BLM Land near Canon City (Garden Park)

Free Public Access

Fremont County

The Garden Park area near Canon City was one of the original Bone Wars collecting grounds in the 1870s-1880s. BLM-managed land in the area allows collection of common invertebrate fossils and small amounts of petrified wood. Vertebrate fossils may not be collected without a permit. The area exposes Morrison Formation and older Paleozoic units.

Dinosaur bone fragmentsMorrison Formation invertebratesPetrified wood

Pierre Shale Exposures (Pueblo Area)

Free Public Access

Pueblo County

Road cuts and natural exposures of the Pierre Shale along the Arkansas River valley near Pueblo yield Cretaceous marine fossils. Baculites (straight ammonites) and large Inoceramus bivalve shells are the most common finds. Concretions in the shale sometimes contain well-preserved ammonites.

BaculitesAmmonitesBivalves (Inoceramus)Shark teeth

Florissant Area (outside National Monument)

Free Public Access

Teller County

Florissant Fossil Beds National Monument itself does not allow collecting, but private land and some BLM parcels in the surrounding area have yielded Eocene insects and plant fossils from the same formation. Access to private sites must be arranged with landowners. The monument is worth visiting for its interpretive displays and giant petrified redwood stumps.

Fossil insectsFossil leavesPetrified wood fragments

Kremmling Cretaceous Ammonite Site

Free Public Access

Grand County

BLM land near Kremmling exposes Pierre Shale with good ammonite and baculite preservation. The BLM has designated some areas for public fossil collecting. Concretions weathering out of the soft shale are the primary targets.

AmmonitesBaculitesBivalves

Legal Rules for Colorado

Fossil collecting on BLM and National Forest land in Colorado is permitted for common invertebrate and plant fossils in reasonable quantities for personal use under the Paleontological Resources Preservation Act. Vertebrate fossils on federal land may not be collected without a research permit. Florissant Fossil Beds National Monument strictly prohibits any collecting. State parks generally do not allow collecting. Dinosaur National Monument and other NPS units prohibit collecting entirely. Always check current BLM field office guidance for specific areas.

Read our full legal guide for federal laws and more details.

Key Geological Formations

  • Morrison Formation (Upper Jurassic)
  • Pierre Shale (Upper Cretaceous)
  • Florissant Formation (Eocene)
  • Niobrara Formation (Upper Cretaceous)

Local Fossil Clubs & Museums