Silver Bow Mining Re-Establishes Underground Access at Its High-Grade Rainbow Block Silver-Zinc Project
NYSE American: SBMT
Overview
Silver Bow Mining Corp. announced that it has re-established underground access at its high-grade Rainbow Block Silver-Zinc Project ("Rainbow Block") through completion of the rehabilitation of the historic Chief Joseph Portal. According to the company, the achievement represents the first underground exploration undertaken in the Butte Mining District, Montana, in approximately 35 years.
The Chief Joseph Portal, which measures approximately 12 feet wide by 14 feet high, provides access to the historic Chief Joseph underground decline and workings at the eastern portion of the Company's Rainbow Block, according to the company. The commencement of the portal rehabilitation was previously disclosed on May 12, 2026, when the Company announced the signing of a contract with MES Mining, a division of Mining & Environmental Services LLC, to rehabilitate and modernize the existing portal and underground decline.
Key Highlights
- The Company has completed rehabilitation of the historic Chief Joseph Portal, re-establishing underground access at the Rainbow Block.
- The Chief Joseph Portal measures approximately 12 feet wide by 14 feet high.
- With underground access re-established, the Company will begin rehabilitating the Chief Joseph Decline to provide safe access to the historic underground workings and establish the infrastructure required for underground exploration.
- Following rehabilitation of the decline, the Company plans to establish underground drill stations on the 200 Level to support resource definition and expansion drilling.
- Approximately 1,000 feet north of the Chief Joseph Portal, the Company has commenced surface preparation for construction of the new Rainbow Portal, measuring 16.5 feet by 16.5 feet, intended to expand and improve underground access to the Rainbow Block.
- The U.S. Mine Safety and Health Administration has issued Federal Mine ID No. 24-02827 to the Company under the name "Silver Bow Mine," authorizing the Company to undertake underground activities at the Rainbow Block.
Strategic/Operational Context
According to the company, underground drilling is expected to provide improved drill positioning allowing more direct access to targeted mineralized structures, with the potential to reduce drill hole lengths, improve drilling efficiency, and accelerate the Company's resource drilling program.
"Re-establishing underground access at the Rainbow Block is an important milestone in Silver Bow Mining's strategy to systematically advance our high-grade Rainbow Block resource," said Travis Naugle, Chairman and Chief Executive Officer. "Once underground, we will have greater exploration flexibility and improved drill access to the mineralized vein systems, accelerating the resource definition and expansion work required to support Silver Bow Mining's next stages of exploration."
"Completion of the Chief Joseph Portal rehabilitation is the first step in safely re-establishing underground operations at Rainbow," said Kevin Shiell, Chief Operating Officer. "Our next priority is rehabilitation of the historic Chief Joseph Decline to provide safe, reliable access to the historic workings and establish the infrastructure required for underground exploration. From there, we plan to establish underground drill stations, providing more direct access to targeted mineralized structures, and improving the efficiency of our resource drilling program."
According to the company, the Rainbow Portal represents a separate component of Silver Bow Mining's longer-term underground infrastructure program and is intended to provide additional access to the underground workings as exploration and, if warranted, development activities advance.
Resources and Financials
The Company's inferred Mineral Resource Estimate is disclosed in a Technical Report Summary prepared in accordance with the requirements of Subpart 1300 of Regulation S-K titled 'Technical Report Summary: Rainbow Block, Butte Mining District, Silver Bow County, Montana, USA' and a NI 43-101 Technical Report titled 'Technical Report on the Rainbow Block Property, Butte Mining District, Silver Bow County, Montana, USA' with an effective date of December 31, 2024, and updated February 3, 2026, prepared by Jacob Anderson, CPG, MAusIMM of Dahrouge Geological Consulting.
- Cut-off grade: 4 opt silver equivalent (AgEq)
- Estimated recoveries: 90% for all metals
- Metal prices used: silver $25.00/oz; gold $2,500/oz; zinc $1.31/lb; lead $0.90/lb
- Rainbow Block flagship resource: 11.48 million tons of inferred resources grading 14.8 opt AgEq (4.28 opt Ag, 0.05 opt Au, 4.59% Zn, and 1.25% Pb)
The scientific and technical information contained in the press release has been reviewed and approved by Phillip Nickerson, PhD, CPG, Vice President of Exploration of Silver Bow Mining Corp., who is a "qualified person" within the meaning of National Instrument 43-101, according to the company.
What to Watch Next
- Rehabilitation of the Chief Joseph Decline to provide safe access to the historic underground workings and establish infrastructure required for underground exploration.
- Establishment of underground drill stations on the 200 Level to support resource definition and expansion drilling.
- Continued surface preparation and construction of the new Rainbow Portal, located approximately 1,000 feet north of the Chief Joseph Portal.
About Silver Bow Mining Corp.
Silver Bow Mining is a minerals exploration company advancing the high-grade Rainbow Block Silver-Zinc Project in Montana's historic Butte Mining District, while targeting a broader suite of U.S.-designated Critical Minerals including copper, manganese, germanium, gallium, indium, antimony, and bismuth. The Company holds approximately 4,193 acres of patented mineral claims and approximately 1,410 acres of surface lands across multiple claim blocks, including the flagship Rainbow Block, which hosts 11.48 million tons of inferred resources grading 14.8 opt AgEq (4.28 opt Ag, 0.05 opt Au, 4.59% Zn, and 1.25% Pb).
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