Hoopes Reservoir: Sillimanite Rockhounding in New Castle County, Delaware

Updated June 2026

Hoopes Reservoir is a mapped rockhounding spot in New Castle County, Delaware. Reported finds include sillimanite. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: New Castle County
State: Delaware
Nearest road: Centerville Road
Postcode: 19807
Coordinates: 39.78549, -75.62546

Geology at Hoopes Reservoir

This spot sits on Wissahickon Schist, mapped as schist and gneiss that formed roughly 540 to 250 million years ago. Metamorphic rock like this is where garnet, staurolite, and kyanite typically grow as the rock recrystallizes under heat and pressure.

Mapped unit: Wissahickon Schist
Age: 540–250 Ma (Paleozoic)
Rock types: schist and gneiss
Elevation: 240 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.

Best time to visit Hoopes Reservoir

Best months: March to November. Typical highs run 84°F in midsummer and 38°F in midwinter, with winter lows near 24°F.

Climate normals: NOAA 1991-2020 monthlies, WILMINGTON PORTER RSCH station (5 mi away).

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 Hoopes Reservoir

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

Sillimanite Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Hoopes Reservoir.

Across the state line from Hoopes Reservoir

Hoopes Reservoir is close enough to the Delaware border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Hoopes Reservoir FAQ

Where is Hoopes Reservoir?+

Hoopes Reservoir is in New Castle County, Delaware, at 39.78549, -75.62546. Nearest road: Centerville Road.

What rocks and minerals can you find at Hoopes Reservoir?+

Hoopes Reservoir is reported to produce Sillimanite.

Is collecting allowed at Hoopes Reservoir?+

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 Hoopes Reservoir?+

A rock hammer, a sieve, and a small shovel work well for garnet-type minerals, which concentrate as resistant grains in soils and creek gravels.

When is the best time to visit Hoopes Reservoir?+

The most comfortable months at Hoopes Reservoir are March to November.

How do I get to Hoopes Reservoir?+

Open the directions link to navigate to 39.78549, -75.62546 in Google Maps. The nearest road is Centerville Road.

More rockhounding in Delaware

See all 13 Delaware spots →

Open Hoopes Reservoir on the map

Use the RockHoundR app for live land overlays, weather, geology, directions, and saved finds.