Key Highlights

  • Silver Bow Mining began underground diamond drilling at its Rainbow Block project in Butte, Montana.
  • It is the first underground exploration drilling in the historic Butte Mining District in more than three decades.
  • The initial drill station sits about 285 feet down the newly built Rainbow Decline from the portal.
  • Drilling focuses on several mineralized vein systems, including follow-up on the Badger and Emily veins.

Silver Bow Mining Corp. (NYSEAM:SBMT) announced on November 11, 2026, that it has started underground diamond drilling at its flagship Rainbow Block Project in Butte, Montana. The work is taking place from a newly constructed decline known as the Rainbow Decline, and it marks the first underground exploration drilling in the historic Butte Mining District in more than 30 years. The company said the program advances its plans to re-establish and expand underground activity at Rainbow Block.

The company is listed on the NYSE American. The program is exploratory, meaning its results will determine whether the vein systems hold enough mineral material to justify further development work and investment.

Where the Drilling Is Taking Place

The initial drill station is roughly 285 feet, or 87 meters, down the new decline from the portal. Drilling is being carried out by NISS Drilling using an electric underground diamond core drill, a method that retrieves cylinders of rock for geologists to inspect. Electric equipment can also reduce the ventilation and fuel handling needed underground, which is one practical advantage of the setup.

The first targets are multiple mineralized vein systems. Follow-up drilling is planned on the Badger and Emily veins, where the company’s 2026 surface drilling returned numerous intercepts of high-grade silver, gold, zinc and lead mineralization. The company also noted other notable critical minerals present in the area, though the scale of those occurrences has not been quantified in the announcement.

Why Underground Work Matters

Surface drilling can show that mineralization exists at depth, but underground drilling allows geologists to test veins more precisely and to sample their structure in greater detail. For a historic mining district like Butte, where earlier generations worked the veins extensively, modern underground data can help distinguish mined-out areas from untested ground.

The company’s plan to systematically evaluate the extensive vein networks at Rainbow Block suggests a long program rather than a single campaign. Each drill hole adds information that shapes the next round of work, and the pace of progress will depend on drilling results, costs and the company’s access to funding.

Economic Assumptions and Risks Ahead

Some earlier economic calculations referenced in the company’s materials used metal prices of $25 per ounce for silver, $2,500 per ounce for gold, $1.31 per pound for zinc and $0.90 per pound for lead, and assumed metallurgical recoveries of 90 percent for each metal. Those assumptions are illustrative and do not represent a resource or reserve estimate, and actual outcomes will depend on drilling results and future prices.

Exploration carries high risk. Many drilling programs do not find economic deposits, and mineral prices can shift sharply. Investors will be looking for assay results from the underground holes, along with any updates on the costs of the program and the company’s financing position.

Final Word

Silver Bow Mining has begun underground drilling at Rainbow Block, the first program of its kind in Butte in more than three decades. The initial focus is on the Badger and Emily veins, where surface drilling has already produced high-grade intercepts. Assay results and updates on the program’s scale will show whether the underground work can turn early encouraging signs into a defined mineral resource.