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Hillsborough River: Brain Coral & Finger Coral Rockhounding in Hillsborough County, Florida

Updated July 2026

The Tampa Bay area is the third of Florida's classic agatized coral regions, and the Hillsborough River drainage yields silicified corals and agate along with brain and finger coral fossils. Much of the finest Tampa Bay agatized coral came from dredging, but river gravel and construction cuts still produce chalcedony-filled coral heads. Agatized coral is an invertebrate fossil and needs no state permit. Reported finds include brain coral, finger coral, agate. Below: coordinates, access notes, nearby spots, and trip-planning links.

Hillsborough River photos

Public image records connected to this spot or its reported material.

1 photo

Rapids over rocks on the Hillsborough River near Tampa, Hillsborough County, Florida

Quick details

Access: Public area
County: Hillsborough County
State: Florida
Nearest road: Temple Terrace Highway
Postcode: 33637
Coordinates: 28.03209, -82.38108

Geology at Hillsborough River

This spot sits on Hawthorn Group, Arcadia Formation, Tampa Member, mapped as limestone that formed roughly 28 to 12 million years ago. Limestone like this typically forms in ancient seas, so marine fossils such as brachiopods, corals, and crinoids tend to weather out of fresh exposures.

Mapped unit: Hawthorn Group, Arcadia Formation, Tampa Member
Age: 28–12 Ma (Late Oligocene to Middle Miocene)
Rock types: limestone
Elevation: 50 ft

Geologic mapping via Macrostrat and the underlying state geological survey maps (CC BY 4.0). Bedrock at the surface can vary within a mapped unit.

Land & collecting status

Generally open to casual rockhounding

Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig.

Public-land rules vary by agency, season, and field office. The RockHoundR app pulls live BLM, USFS, NPS, and tribal overlays so you can see exactly which agency manages the ground at this spot.

Sources & verification

Spot details combine the public RockHoundR location dataset, normalized mineral labels, agency land-status checks in the app, and community submissions. Coordinates are approximate until verified in the field.

Sources: RockHoundR public spot dataset, app land overlays, and local agency review before each trip.

Found at Hillsborough River

Each chip opens all spots that produce that material; the encyclopedia link opens the full ID and field guide.

Nearby rockhounding spots

Other rockhounding spots within driving distance of Hillsborough River.

Hillsborough River FAQ

Where is Hillsborough River?+

Hillsborough River is in Hillsborough County, Florida, at 28.03209, -82.38108. Nearest road: Temple Terrace Highway.

What rocks and minerals can you find at Hillsborough River?+

Hillsborough River is reported to produce Brain Coral, Finger Coral, Agate.

Is collecting allowed at Hillsborough River?+

Generally open to casual rockhounding. Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Hillsborough River?+

A rock hammer, a cold chisel, safety glasses, and newspaper or foam for wrapping finds cover most fossil ground. A trowel and a sieve help in soft exposures.

How do I get to Hillsborough River?+

Open the directions link to navigate to 28.03209, -82.38108 in Google Maps. The nearest road is Temple Terrace Highway.

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