Defiance Quarry: Yellow Calcite & White Calcite Rockhounding in Saint Charles County, Missouri

Updated June 2026

Defiance Quarry is a mapped rockhounding spot in Saint Charles County, Missouri. Reported finds include yellow calcite, white calcite, goethite, marcasite, pyrite, and more. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Saint Charles County
State: Missouri
Nearest road: MO DD
Postcode: 63341
Coordinates: 38.66076, -90.77598

Geology at Defiance Quarry

This spot sits on ground mapped as limestone and siltstone that formed roughly 360 to 325 million years ago. Carbonate rock like this is the classic host for lead, zinc, and fluorite mineralization, which typically follows old cavities and replacement zones.

Age: 360–325 Ma (Mississippian)
Rock types: limestone and siltstone
Elevation: 580 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 Defiance Quarry

Best months: February to November. Typical highs run 88°F in midsummer and 39°F in midwinter, with winter lows near 21°F.

Climate normals: NOAA 1991-2020 monthlies, WELDON SPRING NWS station (6 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 Defiance Quarry

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 Defiance Quarry.

Across the state line from Defiance Quarry

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

Defiance Quarry FAQ

Where is Defiance Quarry?+

Defiance Quarry is in Saint Charles County, Missouri, at 38.66076, -90.77598. Nearest road: MO DD.

What rocks and minerals can you find at Defiance Quarry?+

Defiance Quarry is reported to produce Yellow Calcite, White Calcite, Goethite, Marcasite, Pyrite, Sphalerite, Fossils.

Is collecting allowed at Defiance Quarry?+

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 Defiance Quarry?+

A rock hammer, gloves, and safety glasses cover old mining-district ground. Stay out of shafts and adits; the best specimens typically come from dump piles.

When is the best time to visit Defiance Quarry?+

The most comfortable months at Defiance Quarry are February to November.

How do I get to Defiance Quarry?+

Open the directions link to navigate to 38.66076, -90.77598 in Google Maps. The nearest road is MO DD.

More rockhounding in Missouri

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Open Defiance Quarry on the map

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