Derry: Quartz & Chalcedony Rockhounding in Westmoreland County, Pennsylvania

Plan your visit

Generally open to casual rockhounding

County

Westmoreland County

State

Pennsylvania

Nearest road

Mill Street

Postcode

15627

Coordinates

40.34880, -79.26809

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

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.

Best time to visit Derry

Comfortable months (45 to 90°F highs)

Best months: March to December. Typical highs run 85°F in midsummer and 41°F in midwinter, with winter lows near 24°F.

Climate normals: NOAA 1991-2020 monthlies, LAUREL MTN station (11 mi away), adjusted for elevation.

Geology at Derry

This spot sits on Pottsville Formation, mapped as sandstone and conglomerate that formed roughly 325 to 300 million years ago. Tough silica like agate, jasper, and chert typically weathers out of beds like these and collects as float in drainages and on deflation surfaces.

Mapped unit

Pottsville Formation

Age

325–300 Ma (Pennsylvanian)

Rock types

sandstone and conglomerate

Elevation

1,340 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.

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.

• Pennsylvania Geological Survey
• DCNR state park and state forest rules
• Allegheny National Forest
• Community submissions reviewed against published agency rules