RockWoof
Check access before you go. Most sites listed here are old mines, quarries or prospects, and many are on private land or active mining claims. Get the landowner's permission, check the rules of the agency that manages any public land, and never enter mine workings. Locations are approximate.

Best regions by county

Ranked by the number of USGS-recorded sites, not by access or quality.

  1. Baltimore County: 156 sites; most recorded: Limonite, Chromite, Magnetite
  2. Howard County: 59 sites; most recorded: Marble, Limonite
  3. Frederick County: 51 sites; most recorded: Limonite, Marble
  4. Carroll County: 49 sites; most recorded: Limonite, Carrollite, Chalcopyrite
  5. Harford County: 43 sites; most recorded: Magnetite, Talc, Limonite

Top minerals

  • Limonite: 48 sites
  • Chromite: 9 sites
  • Magnetite: 9 sites
  • Siderite: 6 sites
  • Marble: 5 sites
  • Carrollite: 4 sites
  • Chalcopyrite: 4 sites
  • Quartz: 4 sites

Mineral cards

  • Feldspar

    Mohs 6–6.5. Blocky crystals with flat cleavage faces. Mindat

    97 sites

  • Copper

    Mohs 2.5–3. Native copper is soft and turns green as it weathers. Mindat

    41 sites

  • Gold

    Mohs 2.5–3. Soft, heavy and bright yellow; it doesn’t tarnish. Mindat

    33 sites

  • Magnetite

    Mohs 5.5–6.5. Black and strongly magnetic. Mindat

    15 sites

  • Quartz

    Mohs 7. Six-sided points; smoky quartz is NH’s state gem. Mindat

    14 sites

  • Silver

    Mohs 2.5–3. Native silver tarnishes black. Mindat

    12 sites

  • Pyrite

    Mohs 6–6.5. Brassy “fool’s gold,” often cubic. Mindat

    11 sites

  • Mica

    Mohs 2–3. Peels into thin, flexible, shiny sheets. Mindat

    10 sites

  • Agate

    Mohs 6.5–7. Banded, translucent chalcedony. Mindat

    1 site

  • Galena

    Mohs 2.5–2.75. Heavy, silvery lead ore that breaks into cubes. Mindat

    1 site

Counts are sites whose USGS record mentions the mineral or commodity. Hardness from Mindat.

Minerals most often recorded

Limonite 48Chromite 9Magnetite 9Siderite 6Marble 5Carrollite 4Chalcopyrite 4Quartz 4Molybdenite 3Gold 3Bornite 2Sphalerite 2

Counties

CountySites
Baltimore County156
Howard County59
Frederick County51
Carroll County49
Harford County43
Montgomery County36
Anne Arundel County34
Washington County33
Prince George's County32
Cecil County30
Allegany County30
Garrett County15
Baltimore city13
Calvert County5
Charles County (fewer than 5 sites, no page)2
Wicomico County (fewer than 5 sites, no page)2
Caroline County (fewer than 5 sites, no page)2
Queen Anne's County (fewer than 5 sites, no page)1
Dorchester County (fewer than 5 sites, no page)1
Baltimore (City) County (fewer than 5 sites, no page)1

Mineral guides

Related articles

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