RockWoofSketch map
Woof’s favorite find
Griggstown Mine
We picked it because its USGS record mentions 1 gem or collectible mineral (Tourmaline) and 4 of our card minerals overall. No other named site here scores as high on both counts. USGS lists it as occurrence for Copper. Minerals mentioned: Tourmaline, Magnetite, Pyrite, Copper. Approx. location 40.426, -74.612. USGS record.
Ask first: a USGS record doesn’t mean you can visit. Find out who owns the land and get permission before collecting.
Field cards: what kind of sites?
Produced ore or material at some point in the past.
The mineral was noted here, without development.
Status terms come from USGS MRDS records.
Mineral cards
Copper
Mohs 2.5–3. Native copper is soft and turns green as it weathers. Mindat
11 sites
Magnetite
Mohs 5.5–6.5. Black and strongly magnetic. Mindat
4 sites
Tourmaline
Mohs 7–7.5. Long striated crystals, often black (schorl) or green and pink (elbaite). Mindat
1 site
Pyrite
Mohs 6–6.5. Brassy “fool’s gold,” often cubic. Mindat
1 site
Silver
Mohs 2.5–3. Native silver tarnishes black. Mindat
1 site
Counts are sites whose USGS record mentions the mineral or commodity. Hardness from Mindat.
Minerals recorded here
Copper 5Magnetite 3Chrysocolla 3Cuprite 2Malachite 2Chalcocite 2Chalcopyrite 1Commodities
Copper 8Iron 5Sites
| Site | Commodity | Minerals recorded | Status | Approx. location |
|---|---|---|---|---|
| Griggstown Mine | Copper | Chalcocite, Chalcopyrite, Chrysocolla, Copper, Cuprite, Malachite | Occurrence | 40.426, -74.612 |
| Chimney Rock Mine | Copper | Chalcocite, Chrysocolla, Copper | Past Producer | 40.581, -74.558 |
| American Mine | Copper | Chrysocolla, Copper, Cuprite, Malachite | Past Producer | 40.615, -74.615 |
| Stony Brook Mines | Copper | Copper | Past Producer | 40.633, -74.443 |
| Hoffman Prospect | Copper | Copper | Past Producer | 40.640, -74.627 |
| Janes Mine | Iron | Magnetite | Occurrence | 40.750, -74.583 |
| Auble Mine | Iron | Magnetite | Past Producer | 40.732, -74.644 |
| Auble Mine | Iron | Magnetite | Past Producer | 40.899, -74.644 |
| Griggstown Franklin Mine | Copper | — | Past Producer | 40.428, -74.613 |
| Chimney Rock Mines | Copper | — | Past Producer | 40.582, -74.563 |
| American Bridgewater Mine/Hoffman Mine | Copper | — | Past Producer | 40.617, -74.616 |
| Griggstown Copper Mine | — | — | Past Producer | 40.431, -74.610 |
| Somerville Copper Mine | — | — | Past Producer | 40.607, -74.615 |
| Jane's Mine | Iron | — | Past Producer | 40.752, -74.580 |
| Auble Mine | Iron | — | Past Producer | 40.737, -74.763 |
| Hoffman Copper Mine | — | — | Past Producer | 40.639, -74.627 |
Fossil collections
The Paleobiology Database lists 1 fossil collection records in Somerset County. These are research records, not public dig sites.
Nearby counties
Middlesex County · Hunterdon County · Morris County · Union County · Mercer County
New Jersey mineral guides
- Quartz in New Jersey
- Garnet in New Jersey
- Mica in New Jersey
- Feldspar in New Jersey
- Magnetite in New Jersey
- Pyrite in New Jersey
Back to all New Jersey counties.
How we built this page: we counted named sites in the USGS Mineral Resources Data System (MRDS) for this area, left out sand, gravel, crushed stone, clay pits and unnamed sites, grouped them by Census county, and linked every site to its USGS record. We did not visit these sites, and MRDS does not tell you who owns the land or whether collecting is allowed.
Source: USGS Mineral Resources Data System (MRDS). USGS ceased systematic updates to MRDS around 2011, so status and details may be out of date. Each site links to its USGS record.
Updated