Neptune Mine near Grays Spring: Fluorite Rockhounding in Pima County, Arizona
Updated June 2026
Neptune Mine is a focused Arizona fluorite locality, with Mindat and MRDS records describing a former fluorspar mine where fluorite occurs in lenses and stringers along a schist-granite contact zone. The site adds mineral diversity to the Arizona list because it is a documented industrial-mineral occurrence rather than another chalcedony or placer-gold wash. Reported finds include fluorite. Below: coordinates, access notes, nearby spots, and trip-planning links.
Neptune Mine near Grays Spring photos
Public image records connected to this spot or its reported material.
Map showing Neptune Mine near Grays Spring in Pima County, Arizona
Quick details
- Access
- Public area
- County
- Pima County
- State
- Arizona
- Nearest road
- South Sierrita Mountain Road
- Coordinates
- 31.90639, -111.20806
Geology at Neptune Mine near Grays Spring
This spot sits on granitic rocks, mapped as diorite, alkali granite, and granodiorite that formed roughly 185 to 145 million years ago. Plutonic rock like this weathers slowly into grus and boulders, and the most productive collecting is typically in weathered zones and drainages.
- Mapped unit
- granitic rocks
- Age
- 185–145 Ma (Early Jurassic to Late Jurassic)
- Rock types
- diorite, alkali granite, and granodiorite
- Elevation
- 4,890 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 Neptune Mine near Grays Spring
Best months: August to May. Typical highs run 91°F in midsummer and 58°F in midwinter, with winter lows near 26°F.
Climate normals: NOAA 1991-2020 monthlies, ANVIL RCH station (11 mi away), adjusted for elevation.
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.
State guidance last verified:
- BLM Arizona — Recreational Mineral Collecting
- Arizona Geological Survey
- Arizona State Land Department recreation permits
- Community submissions reviewed against published agency rules
Found at Neptune Mine near Grays Spring
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More rockhounding in Arizona
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