American Marconi Wireless News - Underground Gold Potential Grows at Colosseum

SAN BERNARDINO, CA / ACCESS Newswire / May 15, 2026 / Dateline Resources Limited (ASX:DTR)(OTCQB:DTREF)(FSE:YE1) (Dateline or the Company) is pleased to announce two new broad gold intersections from drill testing of the northeast extension at the North Pit at Colosseum. The Colosseum Gold-REE Project is located in San Bernardino County, California, with the gold Bankable Feasibility Study recently completed.

Drillhole CM26-42 was drilled further to the northeast than previous holes, extending the mineralized zone further to the north and at depth. Drillhole CM25-41 was extended from 149.6m to 437m following positive results in 2025, increasing the mineralized zone by a further 140m downhole.

Highlights

• North Pit NE Extension Confirmed: Drilling has intersected broad zones of mineralisation outside the mineral resource, increasing the potential of the bulk mining underground target:

  • CM25-41 - 287.3m @ 1.05g/t Au from 0m, including 17.7m @ 6.13g/t Au from 19.2m

  • CM26-42 - 214m @ 1.06g/t Au from 0m, including 87.9m @ 1.59g/t Au from 12.2m

• Mineralisation Extends Beyond Mineral Resource Envelope: The new drilling extends several hundred metres beyond the Mineral Resource envelope, demonstrating upside potential.

• Additional Drill Rig to Continue Gold Drilling: Two rigs are targeting rare earth mineralisation at Colosseum via an expanded 18 hole program with a third, Company-owned rig, being recommissioned to allow gold extensions to be tested in parallel.

• REE Samples at Assay Lab: To date, nearly 3,000 metres of rare earth focused diamond drilling has been completed, with holes drilled to up to 745m below surface.

High Density Rocks Correlate with Gravity Anomalies: Specific gravity (SG) analysis of REE drilling indicates high SG readings of greater than 2.8g/cm³, in line with density readings from Mountain Pass carbonatites and well above the 2.65g/cm³ in the breccia pipes.

Dateline's Managing Director, Stephen Baghdadi, commented:

"Gold mineralization at the Colosseum North Pit continues to extend to the northeast and these latest drill intersections again highlight the robust nature of the deposit.

"These broad gold intersections highlight the potential for the definition of an underground deposit at Colosseum that could be exploited following the completion of open pit mining.

"Based on the positive indications so far, the rare earth drilling program has now been expanded to 18 holes. The high-density rocks are an encouraging indicator that we are on the right track."

Colosseum North Pit NE Gold Extensions

Drilling in late 2025 identified a zone in the North Pit at Colosseum demonstrating broad zones of consistent gold mineralization. Previous intercepts in the area included 149.65m @ 1.39g/t Au in CM25-41, 295.64m @ 1.04g/t Au in RC25-035 and 105.15m @ 1.24g/t Au in RC25-037.

As CM25-41 ended in mineralization, it was subsequently re-entered and extended to 437 metres. The mineralized zone was extended by a further 140 metres to 287.3 metres. The overall intersection is 287.3m @ 1.05g/t Au, with a high-grade component of 17.7m @ 6.13g/t Au.

CM26-42 was designed to follow up on the 2025 successes to the northeast of the North Pit and to define the true extents of the breccia pipe. It was designed at 47 degrees true north at a dip of -45 degrees. The hole defined the breccia pipe host lithology out to 292 metres down hole.

CM26-42 results were recently returned showing 214m @ 1.06g/t Au of continuous mineralization, including a higher-grade component of 87.9m @ 1.59g/t Au. Mineralization in the NE Extension remains open at depth and further drilling to define the extents of the breccia pipe and gold mineralization is ongoing.

Key intercepts from recent drilling include:

Note: Intercepts reported above a lower cut-off grade of 0.1 g/t Au. No upper cut-off grade has been applied. All lengths are downhole lengths.

Figure 1: Plan view showing drillholes shown in cross section

Figure 2: Cross-section of the Colosseum deposit illustrating the existing open pit floor and gold intercepts

The recent drill intercepts continue to support the potential for an underground target to the northeast of the North Pit at Colosseum. Mineralization remains open and will be tested further over the coming months. Figure 3 shows the current Mineral Resource blocks to the northeast of the designed open pits, with these new drill results extending outside of these blocks.

Figure 3: Location of the sublevel caving target in relation to the North Pit (Colosseum BFS, 2026)

Colosseum REE Drilling

Drilling of the REE-focused diamond drill program at Colosseum is progressing well, with five holes completed and another two underway. To date, nearly 3,000 metres has been drilled, with all of the holes drilled into the Clark Mountain Fault Zone Target.

Samples have been geologically logged on site and core dispatched to the laboratory for cutting and assaying. Results from the initial batch of samples is expected back in the coming weeks, with further results released regularly soon after.

Specific Gravity Readings

A key characteristic of carbonatite systems is their elevated specific gravity (SG), which commonly ranges between 3.0-3.3g/cm³. This compares to the approximately 2.65g/cm³ SG historically recorded for the gold-bearing breccia pipes at Colosseum.

SG analysis undertaken on selected samples from varying depths and lithologies within the current REE drilling program (including holes CE26-01 and CE26-13) returned elevated SG values ranging from 2.8-3.1g/cm³. The results are considered encouraging, as carbonatite systems can exhibit variable densities depending on alteration, brecciation, fenitization, sulfide content, and proximity to the core of the intrusive system.

Updated Drill Program

Based on further modelling of the gravity data, the REE drill program at Colosseum has been expanded to 18 holes, with 14 holes planned and 4 subject to results.

Further drilling is planned to target a gravity anomaly to the south of the tailings, as well as a magnetic anomaly below the ridge to the east of the Colosseum open pits. This east ridge is also home to both trachyte and fenitized dikes. These dikes are both formed from mantle-derived magmas and are good indicators for deep-seated structures and fluid flow.

Figure 4: Schematic view of the expanded drill program

This press release has been authorized for release by the Board of Dateline Resources Limited.

For more information, please contact:

Stephen Baghdadi
Managing Director
+61 2 9375 2353

Andrew Rowell
Corporate & Investor Relations Manager
+61 400 466 226
[email protected]
www.datelineresources.com.au

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About Dateline Resources Limited

Dateline Resources Limited (ASX:DTR)(OTCQB:DTREF)(FSE:YE1) is an Australian company focused on mining and exploration in North America. The Company owns 100% of the Colosseum Gold-REE Project in California.

The Colosseum Gold Mine is located in the Walker Lane Trend in East San Bernardino County, California and is located 10km north of Mountain Pass rare earth mine. Drill testing the REE potential at Colosseum has commenced.

On 11 May 2026, Dateline announced that the BFS economics for the Colosseum Gold Project generated a pre-tax NPV₅ of US$785 million and a pre-tax IRR of 49.5% using a gold price of US$4,200/oz.

Dateline has also acquired the high-grade Argos Strontium Project, also located in San Bernadino County, California. Argos is reportedly the largest strontium deposit in the U.S. with previous celestite production grading 95%+ SrSO₄.

In March 2026, Dateline consolidated the Music Valley Heavy Rare Earth Project in Riverside and San Bernardino Counties, California. The region has known HREE mineralisation from USGS rock chip sampling, however it has not been subjected to modern exploration techniques.

Forward-Looking Statements

This announcement may contain "forward-looking statements" concerning Dateline Resources that are subject to risks and uncertainties. Generally, the words "will", "may", "should", "continue", "believes", "expects", "intends", "anticipates" or similar expressions identify forward-looking statements. These forward-looking statements involve risks and uncertainties that could cause actual results to differ materially from those expressed in the forward-looking statements. Many of these risks and uncertainties relate to factors that are beyond Dateline Resources' ability to control or estimate precisely, such as future market conditions, changes in regulatory environment and the behavior of other market participants. Dateline Resources cannot give any assurance that such forward-looking statements will prove to have been correct. The reader is cautioned not to place undue reliance on these forward-looking statements. Dateline Resources assumes no obligation and does not undertake any obligation to update or revise publicly any of the forward-looking statements set out herein, whether as a result of new information, future events or otherwise, except to the extent legally required.

Competent Person Statements

Sample preparation and any exploration information in this announcement is based upon work reviewed by Mr Greg Hall who is a Chartered Professional of the Australasian Institute of Mining and Metallurgy (CP-IMM). Mr Hall has sufficient experience that is relevant to the style of mineralization and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the 2012 Edition of the "Australasian Code for Reporting Exploration Results, Mineral Resources and Ore Reserves" (JORC Code). Mr Hall is a Non-Executive Director of Dateline Resources Limited and consents to the inclusion in the report of the matters based on this information in the form and context in which it appears.

SOURCE: Dateline Resources Limited

View the original press release on ACCESS Newswire

T.Ward--AMWN