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    Dakota Gold’s Richmond Hill assays: project economics and pit design notes

    July 7, 2026|

    Reviewed by Joe Ashwell

    Dakota Gold’s Richmond Hill assays: project economics and pit design notes

    First reported on MINING.com

    30 Second Briefing

    New drilling at Dakota Gold’s Richmond Hill project in South Dakota has returned high-grade intercepts inside the planned open pit, including 26 metres at 11.36 g/t gold and 14.92 g/t silver from ~75 metres in hole RH26C-432 and 38 metres at 2.89 g/t gold and 8.18 g/t silver from ~145 metres in RH26C-437. The 2026 programme totalled 17,273 metres across 112 infill, expansion and geotechnical holes, with assays from 350+ holes feeding a prefeasibility study due by 31 December and long-lead items such as an electrical substation already queued with Black Hills Energy. Richmond Hill, a large oxide gold system amenable to open-pit and heap leach, carries 244.7 Mt measured and indicated at 0.46 g/t Au and 4.83 g/t Ag (3.6 Moz Au, 38 Moz Ag), with an S-K 1300 Initial Assessment outlining 2.6–3.9 Moz Au production over 28 years and a post-tax NPV of $1.6–2.1 billion at a 55–59% IRR.

    Technical Brief

    • Expansion hole RH26C-452 intersected 16 m at 1.63 g/t Au and 12.03 g/t Ag from 79 m.
    • Near-surface hole RH26C-448 returned 22 m at 0.61 g/t Au and 55.85 g/t Ag from 11 m.
    • 2026 drilling comprised 112 holes over 17,273 m, including dedicated geotechnical holes for pit and infrastructure design.
    • Assay dataset now exceeds 350 holes across 2025–26, providing dense spacing for PFS resource and pit optimisation.
    • Expansion drilling in the northeast project area remains open in all directions, indicating potential for further pit growth.
    • Electrical substation identified as the longest-lead critical item, with a construction slot secured via Black Hills Energy.
    • Richmond Hill lies ~320 km west of Pierre within a 180 km² land package near the historic Homestake mine.
    • S-K 1300 Initial Assessment (July) underpins economics: post-tax NPV US$1.6–2.1 billion, IRR 55–59%, initial capex US$384 million.
    • Initial resource (Feb 2025) totals 244.7 Mt M&I at 0.46 g/t Au and 4.83 g/t Ag plus 230.6 Mt inferred at 0.35 g/t Au and 3.09 g/t Ag.
    • CEO Robert Quartermain previously developed the Brucejack mine before its ~C$3.5 billion sale to Newcrest (now Newmont).

    Our Take

    With measured and indicated resources of 244.7 million tonnes at 0.46 g/t gold and 4.83 g/t silver, Richmond Hill sits at the low-grade, bulk-tonnage end of the gold spectrum in our Mining database, which makes the reported 11.36 g/t and similar intercepts particularly important for lifting early-phase economics and justifying the US$384 million initial cost profile.

    The previous Richmond Hill drilling piece from 17 March 2026 in our coverage also highlighted step-out success to the north; combined with the current 112-hole 2026 programme and more than 350 holes already completed, this signals a deliberate push to convert a very large inferred inventory (230.6 million tonnes) into mineable reserves ahead of the S-K 1300 Initial Assessment and PFS work.

    Dakota Gold’s potential 2.6–3.9 million oz life-of-mine production in South Dakota is modest compared with senior producers like Newmont (also referenced in the article facts), but the 55–59% post-tax IRR range and sub-US$400 million capex put Richmond Hill into the kind of high-return, mid-scale project bracket that larger gold companies in our database have recently been targeting for bolt-on growth rather than mega-projects.

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    Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.

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