Epithermal volcanic Au-Ag
Eldorado / Keyhole quartz-calcite veins
Metals on this play: au, ag, cu, pb, zn
Calibration
Techatticup Mine, Eldorado Canyon, Clark County, NV. ~175k oz Au 1860–1900 plus later production; district 100,600 oz Au and 2.36 Moz Ag 1907–1954. Hansen 1962; Longwell et al. 1965 NBMG Bull. 62; Kern, Drobeck & Jenkins Nelson district geology.
The trap
Host. Precambrian gneiss/schist, Miocene volcanics (Patsy Mine, Golden Door, Mount Davis), Nelson quartz monzonite, Keyhole leucogranite. Quartz-calcite fissure veins and stockworks at stock margins.
Trap. Epithermal boiling/mixing in steep quartz-calcite veins. Native gold, silver, pyrite, galena, chalcopyrite, sphalerite. Chlorargyrite in oxidized Savage-type shoots. Same plumbing on both flanks of the Eldorado Mountains.
What a hit looks like. Quartz-calcite vein or iron-stained breccia in granite, gneiss, or andesite. Green Cu stain. High Au+Ag on XRF of the vein, not of pretty petroglyph granite. Do not chip the panels.
Wrong mountain
This is Techatticup, not Silver Reef and not Treasure Hill. Do not XRF petrified wood. Do not hunt a 24-lb nugget in Eldorado Canyon. Do not chip Keyhole rock art. The next walk is the west-flank Keyhole leucogranite and the US-95 saddle veins — same stock as Nelson, other side of the mountain.
- Prospect Mountain quartzite / Treasure Hill — Play F. Different mountain, different host.
- Combined Metals limestone — Play E.
- Sandstone + wood — Plays A–D.
- Osceola-class nugget gulch — Play H. Eldorado has a small placer; it is not the 24-lb story.
- Sedimentary wad Mn in Muddy Creek tuff (Three Kids) — Play J.
- Keyhole petroglyph panels, pictographs, and cupules — archaeological site. Do not sample them. Walk veins in granite away from the art.
- Lake Mead NRA interior / Ireteba Peaks Wilderness core — access-killed, still mapped so you see why.
How to use the score
The score orders the day. It is a walk sort. It is not an assay, a mining claim, or permission to enter. Killed ground stays on the map so the boundary is visible. Private land, tribal land, and park interiors stay off the walk.