RockWoofSketch map
Woof’s favorite find
Holmes Mine
We picked it because its USGS record mentions 1 gem or collectible mineral (Quartz) and 3 of our card minerals overall. That ties with 1 other site(s), so we broke the tie by mine status (past producers first), then USGS record quality, then name. USGS lists it as unknown for Lead. Minerals mentioned: Quartz, Pyrite, Galena. Approx. location 42.814, -91.151. 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 not recorded.
Status terms come from USGS MRDS records.
Mineral cards
Galena
Mohs 2.5–2.75. Heavy, silvery lead ore that breaks into cubes. Mindat
8 sites
Quartz
Mohs 7. Six-sided points; smoky quartz is NH’s state gem. Mindat
2 sites
Pyrite
Mohs 6–6.5. Brassy “fool’s gold,” often cubic. Mindat
2 sites
Fluorite
Mohs 4. Cubes in purple, green or yellow; many glow under UV. Mindat
1 site
Counts are sites whose USGS record mentions the mineral or commodity. Hardness from Mindat.
Minerals recorded here
Galena 8Smithsonite 1Fluorite 1Sphalerite 1Commodities
Lead 17Phosphorus-Phosphates 10Zinc 4Fluorine-Fluorite 1Sites
| Site | Commodity | Minerals recorded | Status | Approx. location |
|---|---|---|---|---|
| Volga Occurrence | Phosphorus-Phosphates, Fluorine-Fluorite, Zinc | Fluorite, Sphalerite | Past Producer | 42.807, -91.545 |
| Sny Magill Mines | Lead | Galena | Past Producer | 42.949, -91.185 |
| Quarry | Lead | Galena | Past Producer | 42.938, -91.178 |
| Occurrence | Lead | Galena | Past Producer | 42.791, -91.210 |
| Spellman Farm | Lead | Galena | Occurrence | 42.754, -91.362 |
| Kann Mine | Lead | Galena | Past Producer | 42.817, -91.168 |
| Holmes Mine | Lead | Galena | Unknown | 42.814, -91.151 |
| Kann Mine | Lead | Galena | Unknown | 42.818, -91.166 |
| Indian Lead Mines | Lead | Galena | Occurrence | 42.905, -91.477 |
| Elkader Mine | Zinc | Smithsonite | Past Producer | 42.874, -91.380 |
| Roadcut | Phosphorus-Phosphates | — | Past Producer | 42.949, -91.393 |
| Roadcut | Phosphorus-Phosphates | — | Past Producer | 42.865, -91.252 |
| Quarry | Phosphorus-Phosphates | — | Past Producer | 42.739, -91.384 |
| Roadcut | Phosphorus-Phosphates | — | Past Producer | 42.773, -91.208 |
| Roadcut | Phosphorus-Phosphates | — | Past Producer | 42.750, -91.254 |
| Roadcut | Phosphorus-Phosphates | — | Past Producer | 42.693, -91.287 |
| Quarry | Phosphorus-Phosphates | — | Past Producer | 42.679, -91.038 |
| Quarry | Phosphorus-Phosphates | — | Past Producer | 42.796, -91.355 |
| Outcrop | Phosphorus-Phosphates | — | Past Producer | 42.680, -91.116 |
| Burtletts Diggings | Lead | — | Past Producer | 42.715, -91.064 |
| Panther Hollow Mines | Lead | — | Past Producer | 42.675, -90.976 |
| Old Indian Mines | Lead | — | Past Producer | 42.899, -91.458 |
| Buena Vista Mines | Lead | — | Past Producer | 42.671, -90.961 |
| Lunders Diggings | Lead | — | Past Producer | 42.697, -91.045 |
| Guttenberg Mines | Lead | — | Past Producer | 42.798, -91.123 |
| Tete Des Morts Subdistrict | Lead, Zinc | — | Past Producer | 42.380, -90.510 |
| Guttenberg Subdistrict | Lead | — | Past Producer | 42.808, -91.128 |
| Sherrill Mound Subdistrict | Zinc, Lead | — | Past Producer | 42.604, -90.822 |
Fossil collections
The Paleobiology Database lists 3 fossil collection records in Clayton County. These are research records, not public dig sites.
Nearby counties
Delaware County · Dubuque County · Fayette County · Jackson County · Allamakee County
Iowa mineral guides
Back to all Iowa 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