Silver Bow Mining begins underground drilling at Montana’s Rainbow Block The initial underground drill station is located about 285ft down the Rainbow Decline from its portal. Credit: Wlad74/Shutterstock.com. · Mining Technology · Wlad74/Shutterstock.com. Shree Mishra Thu, November 12, 2026 at 5:33 AM EST 3 min read SBMT 0.00% SI=F -1.38% GC=F -1.02% Silver Bow Mining has started underground diamond drilling at its Rainbow Block Project in Butte, Montana, US, representing the first such activity in the Butte Mining District for more than 30 years.
The company announced that drilling has begun from a dedicated drill station within the newly constructed Rainbow Decline, at an elevation of 6,210ft.
The initiative aims to evaluate multiple mineralised vein systems, including the Badger and Emily veins.
According to Silver Bow Mining, earlier surface drilling in these areas highlighted the presence of high-grade silver, gold, zinc, lead, and other critical minerals.
The current programme seeks to build on these results by targeting sections of 12 mineralised veins that extend beyond the company's present mineral resource estimate at the Rainbow Block.
The initial underground drill station is located about 285ft (87m) down the Rainbow Decline from its portal.
Contractor NISS Drilling is carrying out the work with the use of a KMN1.4 electric underground diamond core drill.
The work forms part of a broader exploration campaign, including plans to drill 30,000ft from the Rainbow and Chief Joseph declines in 2026 and 2027.
Silver Bow Mining received approval from the Montana Department of Environmental Quality in May to proceed with the Rainbow Decline and its associated 6,000ft of planned underground development, which will connect with the existing Lexington Tunnel level.
By August 2026, preparations for a new Rainbow Portal had begun, and underground access via the Chief Joseph Portal had been restored.
Silver Bow Mining chairman and CEO Travis Naugle said: "In my career, I have never seen a setup like this: from a single underground station, we can drill in virtually every direction to test 12 separate vein targets, each an extension beyond our current Mineral Resource estimate.
"With high-grade results from numerous veins already in hand from this year's surface programme, we are doing what we committed to do: following up from underground, seeking to advance growth in the Rainbow Block Mineral Resource and evaluating the project's future development potential."
The company said that underground drilling enables improved drill orientations and shorter drilling distances, providing greater flexibility to assess the continuity of targeted veins.
The Rainbow and Chief Joseph declines are expected to serve as key platforms for ongoing exploration as underground development progresses.
The current drilling campaign is intended to expand and upgrade the mineral resource while providing geological information to inform future project planning.
In August this year, Silver Bow Mining signed a definitive asset purchase agreement to acquire the Jefferson County Metallurgical Complex in Montana from Montana Goldfields and Montana Tunnels Mining.
"Silver Bow Mining begins underground drilling at Montana's Rainbow Block" was originally created and published by Mining Technology, a GlobalData owned brand.
