Butte's veins were mined for a century — mostly from the bottom up, for copper. Silver Bow Mining Corp. (NYSE American: SBMT) is testing what Anaconda left in the tops of those veins, and on November 5 it reported the first assays from the Emily Vein at its Rainbow Block Project: high-grade silver-gold-zinc-lead in ground that sits above the historical workings.
- SBM26-08 — Emily Vein: 11.2 metres grading 312.7 g/t AgEq (51.5 g/t Ag, 0.08 g/t Au, 5.81% Zn, 1.80% Pb, 15.95 ppm indium) from 369.3 metres, including 3.6 metres grading 462.7 g/t AgEq (92.4 g/t Ag, 0.16 g/t Au, 8.48% Zn, 1.99% Pb, 25.95 ppm indium). Indium is excluded from the AgEq calculation.
- SBM26-05 — Emily Vein: 2.0 metres grading 482.7 g/t AgEq (88.4 g/t Ag, 0.99 g/t Au, 6.25% Zn, 2.87% Pb) from 286.3 metres, near the Emily–Rainbow vein intersection.
- SBM26-05 — Rainbow Vein: 1.3 metres grading 680.8 g/t AgEq (382.7 g/t Ag, 0.41 g/t Au, 5.09% Zn, 3.02% Pb); the same hole cut an unnamed vein at 1.4 metres grading 252.1 g/t AgEq.
- The setting: the Emily Vein sits approximately 245 metres (800 feet) north of the Badger Vein. Anaconda records show it was mined principally for copper between roughly 1,000 and 3,000 feet depth; the upper 1,000 feet was left largely unmined — the portion both holes intersected.
- Outside the resource: no Emily Vein mineralization is included in the current Rainbow Block Inferred Mineral Resource estimate. All intervals are down-hole lengths; estimated true widths are 60–80% of reported lengths in SBM26-05 and 30–35% in SBM26-08.
- Program status: 22,725 feet of the 25,000-foot surface diamond drilling program are complete, and the company is preparing to begin underground drilling shortly.
The Anaconda mapbook strategy
This is the same play that produced Silver Bow's earlier Badger Vein and Black Rock results: use historical Anaconda Mining Company data to target the parts of the Butte vein system the old operators skipped. Vice President of Exploration Dr. Phillip Nickerson noted both holes hit mineralization in the largely unmined upper Emily, above the historical workings, and that SBM26-08 also returned elevated indium — a U.S.-designated critical mineral — at up to 25.95 ppm over 3.6 metres.
Chairman and CEO Travis Naugle: "The Emily Vein adds another high-grade target at the Rainbow Block and underscores the exploration potential in the upper portions of Butte veins that Anaconda Mining left largely unmined." With the surface program nearly complete, the company plans to test the system from underground positions as well, building toward an expanded Rainbow Block resource.
The honesty box
These are two holes in a vein with no current resource attribution — first assays establish that the upper Emily is mineralized, not how continuous or large it is. The true width in SBM26-08 is only an estimated 30–35% of the 11.2-metre down-hole interval, so the headline width overstates the vein thickness in that hole. AgEq grades are calculated by the company using $25.00/oz silver, $2,500/oz gold, $1.31/lb zinc and $0.90/lb lead with assumed 90% recoveries for all metals — recoveries the release states have not been established for these specific intervals. The historical Anaconda mining depths are company-cited historical records, reported here as the company states them.
What to watch
The final ~2,275 feet of the surface program and the start of underground drilling; follow-up holes along the Emily Vein testing whether the SBM26-05 and SBM26-08 intercepts connect; and the updated Rainbow Block resource work, where Emily mineralization would first have to be drilled to density before it can be included.