Rubicon Minerals Reports a Material Increase in Mineral Resources, including a 113% Growth in Measured and Indicated Resources, at the Phoenix Gold Project

TSX: RMX | OTCQX: RBYCF

TORONTO, April 30, 2018 /CNW/ - Rubicon Minerals Corporation (TSX: RMX | OTCQX: RBYCF) ("Rubicon" or the "Company") is pleased to report an updated Mineral Resource Estimate ("2018 Mineral Resource Estimate") for the Phoenix Gold Project (the "Project"). The Company plans to file an updated NI 43-101 Technical Report for the Project within 45 days.

Table 1: 2018 Mineral Resource Estimate at 3.0 grams per tonnes of gold ("g/t Au") Cut-Off Grade¹ - Effective April 30, 2018

• Effective date for this Mineral Resource is April 30, 2018
• Mineral Resource Estimate uses a break-even economic cut-off grade of 3.0 g/t Au based on assumptions of a gold price of US$1,300 per ounce, an exchange rate of US$/C$ 0.77, mining cash costs² of C$97/t, processing costs of C$20/t, G&A of C$5/t, sustaining capital C$10/t, refining, transport and royalty costs of C$53/oz, and average gold recoverability of 92%
• Mineral Resource Estimate reported from within an envelope accounting for mineral continuity
• Mineral Resources are not Mineral Reserves and do not demonstrate economic viability
• There is no certainty that all or any part of this Mineral Resource will be converted into Mineral Reserve
• All figures are rounded to reflect the relative accuracy of the estimates and totals may not add correctly

Table 2: Comparison between 2018³ and 2016⁴ Estimated Quantities at Reported Cut-Off Grades – 3.0 g/t Au (2018 Mineral Resource Estimate), 3.5 g/t Au and 4.0 g/t Au(Historic 2016 Mineral Resource Estimate⁴)

Key Points:

Based on a 3.0 g/t Au cut-off grade:

• Measured and Indicated Resources increased 113% to 281,000 ounces of gold compared to 2016 Indicated Resources (Measured Resources were not estimated in 2016) of 132,000 ounces of gold; Measured and Indicated grades increased 12% to 6.37 g/t Au compared to 2016 Indicated gold grades of 5.71 g/t Au;
• Inferred Resources increased 80% to 749,000 ounces of gold compared to 2016 Inferred Resources of 415,000 ounces of gold; Inferred grades increased 16% to 6.00 g/t Au compared to 2016 Inferred grades of 5.18 g/t Au; and
• The increase in Mineral Resources is mainly attributed to, and supported by, a re-interpretation of geological and structural controls on mineralization along with recognizing the potential for larger scale mining, rather than focusing entirely on a narrow-vein mining plan, which resulted in broader mineral domains.

General observations and commentary

• Reported Measured Resources for the first time in the history of the Project;
• New interpretation of the geological and structural controls on gold mineralization;
• Considerations for potential bulk mining methods;
• 2018 Mineral Resource Estimate includes exploration data up to November 30, 2017 (which includes 23,500 metres ("m") of oriented drilling);
• Early observations from the 2018 infill drilling and underground development samples from test mining appear to show grades consistent with the 2018 Mineral Resource Estimate, but it is still too early to complete mining reconciliations and draw conclusions;
• Potential to further upgrade the classifications and expand the 2018 Mineral Resources with data from 5,000 m of drilling completed in the fourth quarter of 2017 and activities from the 2018 Exploration Program, including test mining and an additional 24,000 m of drilling; and
• Conference call with Rubicon's senior management will be held today at 10:00am ET. Canada/ U.S. toll-free dial-in number +1(888) 231-8191, International dial-in number +1 (647) 427-7450, webcast link: https://event.on24.com/wcc/r/1665362/858E306DCFE37785798419DFE29660AE.

Rubicon President and Chief Executive Officer George Ogilvie, P.Eng., stated, "On the back of a successful 2017 Exploration Program, we are pleased to deliver the 2018 Mineral Resource Estimate, which demonstrates a significant increase in ounces, grades, and tonnes at the Phoenix Gold Project. This is an important step forward towards potentially advancing the Project to a viable commercial operation. We are uniquely positioned compared to other junior gold explorers because we have substantial mine infrastructure in place, including a new state-of-the-art 1,250-tonne per day mill, a completed tailings management facility, a 200-person camp, earth and civil works in place, a fully commissioned hoist and headframe, a shaft that is approximately 730-metres deep, mobile equipment and more than nine kilometres of underground development. We also have approximately C$687 million in tax loss pools that could be utilized in a potential viable commercial operation scenario. I am also pleased to report that the Company deployed shareholder capital efficiently, resulting in a finding cost of approximately C$7 per ounce⁵."

"We delivered the 2018 Mineral Resource Estimate ahead of schedule mainly because we saw significant growth in the Mineral Resources after we finalized our internal estimates. Other factors, such as finalizing the structural geology interpretation, the encouraging initial results from the closely spaced 2018 test stope infill drilling and development samples during test mining, and the review by two reputable external consultants in Golder Associates and Tim Maunula and Associates Consulting, give us additional confidence in the 2018 Mineral Resource Estimate."

"We are pleased with the progress achieved to-date and we believe there is still further potential to improve upon the 2018 Mineral Resource Estimate. Our current exploration and test mining activities provides us with the potential opportunity to significantly enhance both the quantities and the classifications of the 2018 Mineral Resource Estimate at a future date."

2018 Geological Model of the F2 Gold Deposit

The 2018 geological model benefits from information that was not previously available in 2016, including approximately 3,500 m of oriented structural drilling, 20,000 m of oriented infill and step-out drilling, the structural re-logging of 10,000 m of historical core, and detailed structural mapping carried out in 2017. The Company believes the new geological information provides a better understanding of the structural and lithological controls on the distribution of the gold mineralization, its grade, and its continuity, of the F2 Gold Deposit. On March 12, 2018, Rubicon, Golder Associates Ltd. ("Golder") and peer reviewer T. Maunula and Associates (together, "Consultants") provided an updated preliminary interpretation of the structural geology of the F2 Gold Deposit ("Structural Interpretation"), which has since been finalized. According to the Structural Interpretation, the primary controls on the gold mineralization are the well-established dextral Riedel vein system of quartz-actinolite veins (the "Riedel vein system") that occur within the biotite and silica altered basaltic mafic volcanic flows ("HiTi Basalt Units") (the main host rock for gold mineralization) and the quartz-feldspar porphyry felsic dykes and sills ("Felsic Intrusive Units") (to a lesser extent). The Riedel vein system demonstrates greater continuity of gold mineralization within the HiTi Basalt Units compared to the 2016 structural interpretation. Rubicon believes the Structural Interpretation has allowed for the evaluation of bulk mining methods for the Project. For further details on the Structural Interpretation, please refer to the Rubicon news release on March 12, 2018.

Using the Structural Interpretation as the basis for an updated geological model, the Company and its Consultants were able to interpolate a greater volume of gold mineralization within the HiTi Basalt Units. This resulted in a significant increase in the mineralized tonnes and ounces throughout the deposit compared to the 2016 Mineral Resource estimate. Rubicon believes additional exploration work (drilling, development, test mining and bulk sampling) is required to further improve and reconcile the geological model for the F2 Gold Deposit.

2018 Mineral Resource Estimate

The 2018 Mineral Resource Estimate⁶ (see Table 1 above) benefits from 483,303 m⁷ of core drilling in 1,343 drill holes carried out from February 2008 to November 2017, along with the re-logging of approximately 10,000 m of historical core, detailed structural mapping, and existing data from development mapping and underground wall sampling (chip samples). The 2018 Mineral Resource model covers a strike length of approximately 1,200 m and depths up to 1,350 m and remains open along strike and at depth. The 2018 Mineral Resource Estimate excludes the crown pillar, depleted resources, and information below the 1,350 m elevation.

The 2018 Mineral Resource Estimate was evaluated using a geostatistical block modelling approach constrained by mineral and stratigraphic domains interpreted from the drill hole and mapping data. The block model grades were interpolated using inverse distance cubed ("ID3"), which the Company evaluated as the most representative method. Rubicon assessed other grade interpolation methodologies, including ordinary kriging ("OK") and inverse distance squared ("ID2"), and determined that the ID3 estimates controlled grade smoothing the best and achieved an appropriate grade-tonnage profile relative to the characteristics of the deposit. Density data was assigned based on average values for each stratigraphic unit.

The block model was classified in accordance with Canadian Institute of Mining, Metallurgy and Petroleum ("CIM") Definition Standards for Mineral Resources and Mineral Reserves (May 2014). Drill spacing for Mineral Resources in the Measured, Indicated, and Inferred categories were approximately up to 20 m, 20-to-40 m, and 40-to-80 m centres, respectively, where geology and grade continuity were reasonably understood. Measured Resources required a minimum of a 20 m by 20 m drill spacing with sub-level development, mapping, chip samples and supported by reconciliation where available. Measured and Indicated Resources are all located near existing underground infrastructure and development.

The Mineral Resources are sensitive to the selection of reporting assumptions. The sensitivity of the Mineral Resource estimates to the selection of cut-off grade is summarized as grade tonnage data in Table 3 below. The classified Mineral Resources reported by underground level are tabulated in Table 6 (at the end of this news release). Please see Diagrams 1, 2, and 3 (at the end of this news release) showing the conceptual plan view and cross sections of Zones 1 and 2 (the two main mineral domains) of the 2018 Mineral Resource blocks in the Measured, Indicated, and Inferred categories, and Exploration Target areas.

At a 3.0 g/t Au cut-off grade for the 2018 Mineral Resource Estimate, Rubicon is evaluating a potential bulk mining scenario for the F2 Gold Deposit. The Company is currently testing the sub-level long-hole mining method for its three test stopes and anticipates extracting a bulk sample between 25,000 to 30,000 tonnes, which will be processed at the Company's mill. Rubicon intends to reactivate its mill later this year. Observations and results from its test mining activities will allow the Company to confirm the amenability of possible bulk mining methods.

Table 3: 2018 Mineral Resource Sensitivity Analysis at Potential Mining Cut-off Grades⁸ 

Comparison Between the 2018 and 2016 Minerals Resource Estimates⁹

The 2018 Mineral Resource Estimate has been developed by building on the Company's historical exploration activity. The 2018 Mineral Resource Estimate included additional data from the 2017 Exploration Program, which was not available during the determination of the 2016 Mineral Resource Estimate⁹. At the reporting cut-off grade of 3.0 g/t Au, the 2018 Measured and Indicated Resources' tonnes, grade, and gold ounces increased by 91%, 12% and 113%, respectively, compared to the 2016 Indicated Mineral Resources (Measured Resources were not estimated). The 2018 Inferred Mineral Resources' tonnes, grade, and gold ounces increased by 56%, 16%, and 80%, respectively, compared to the 2016 Inferred Resources. The expansion of the Mineral Resources is mainly attributed to, and supported by, a re-interpretation of geological and structural controls on mineralization along with recognizing the potential for larger scale mining, rather than focusing entirely on a narrow-vein mining plan, which resulted in broader mineral domains. The comparison between the 2018 Mineral Resource Estimate and 2016 Mineral Resource Estimate are summarized in Table 2 (above). The Company believes it has deployed more reasonable controls and estimation parameters to produce a representative geological model and 2018 Mineral Resource Estimate. A summary of the key parameters used for the 2018 Mineral Resource Estimate and comparison to the 2016 Mineral Resource Model is included in Table 4 below. 

Table 4: Summary of Key Parameters that Contributed to the Changes in Mineral Resources between 2018 and 2016⁹

Please refer to Table 5 at the end of the news release for further details on the geological modelling and high-grade treatment strategies, including top-cut values and coefficients of variation ("CV") for each sample population.  

Next Steps

The Company believes it can potentially improve upon the 2018 Mineral Resource Estimate in the following areas:

• Targeted infill and step-out drilling in areas containing Inferred Resources and Exploration Targets¹⁰: Rubicon intends to potentially convert Inferred Resources to Indicated Resources by drilling areas in the mid-to-upper levels of the deposit where existing drill spacing is on 40-m centres or more. Furthermore, Rubicon has identified Exploration Target areas¹⁰ (greater than 80-metre centres) potentially between 500,000 and 800,000 tonnes of sparsely drilled mineralized material with grades potentially between 5.0 to 7.0 g/t Au where the Company intends to infill drill.
• Model reconciliation based on 25,000 to 30,000 tonnes of bulk sample processing: The results from the bulk sampling program will be used to reconcile and validate any future Mineral Resource Estimate, and potentially increase confidence in the modelling process and Mineral Resources. Early observations from infill drilling and samples from the test stopes show that grades appear to be consistent with the 2018 Mineral Resource Estimate, although no conclusions can be made at this time;
• Evaluating McFinley and Close Proximity Targets: Rubicon is evaluating Mineral Resource data from the historic McFinley Deposit, located near existing underground development at the Project, using current standards and parameters, which could be potentially included in any future Mineral Resource Estimate. The Company is also evaluating historical drill data from its Close Proximity Targets (Peninsula, CARZ, and Island Zones) located within two kilometres northeast of the Project, which could possibly be included in any future updated Mineral Resource Estimate.
• F2 Gold Deposit remains open at depth and along strike: Historical drilling intersected high-grade intercepts to a depth of 1,600 m below surface, well below the bottom of the 2018 Mineral Resource Estimate at 1,350 m elevation. These intercepts warrant follow up drilling in the future.

Conference Call Details

The Company's senior management team will host a conference call today, Monday, April 30, 2018 at 10:00 am ET (7:00 am PT) to discuss the news release. Participants in Canada and the United States may join the conference call by dialing toll free +1 (888) 231-8191 or +1 (647) 427-7450 for calls outside Canada and the United States or via webcast:
https://event.on24.com/wcc/r/1665362/858E306DCFE37785798419DFE29660AE.

A recorded playback of the conference call can be accessed on the Company's website at www.rubiconminerals.com.

Qualified Persons and Quality Assurance and Quality Control (QA/QC)

The content of this news release has been read and approved by George Ogilvie, P.Eng., President and CEO for Rubicon, Brian Thomas, P.Geo., and Jerry DeWolfe, P.Geo., M.Sc. for Golder, and Tim Maunula, P.Geo. for T. Maunula & Associates Consulting Inc. All four are Qualified Persons as defined by NI 43-101.

Underground drilling was conducted by Boart Longyear Drilling of Haileybury, Ontario and was supervised by the Rubicon exploration team. Oriented core drilling was performed using the Boart Longyear TruCore™ orientation system. All assays reported are uncut unless otherwise stated. All samples reported herein were performed by SGS Mineral Services of Red Lake, Ontario, an independent lab with ISO/IEC 17025-2005 standards. All NQ core assays reported were obtained by fire assay with AA-finish or using gravimetric finish for values over 10.0 g/t Au.

Intercepts cited do not necessarily represent true widths, unless otherwise noted, however drilling is generally intersecting interpreted mineralized zones at a high angle. True width determinations are estimated at 65-80% of the core length intervals for the 305-metre level drilling, and estimated at 75-95% of the core length for the 610- and 685-metre level drilling. Rubicon's quality control checks include insertion of blanks, certified reference standards and blind duplicates to monitor laboratory accuracy and precision.

About Rubicon Minerals Corporation
Rubicon Minerals Corporation is an advanced gold exploration company that owns the Phoenix Gold Project, located in the prolific Red Lake gold district in northwestern Ontario, Canada. Additionally, Rubicon controls over 280 square kilometres of prime exploration ground in Red Lake and more than 900 square kilometres of mineral property interests in the emerging Long Canyon gold district that straddles the Nevada-Utah border in the United States. Rubicon's shares are listed on the Toronto Stock Exchange (RMX) and the OTCQX markets (RBYCF). For more information, please visit our website at www.rubiconminerals.com.  

RUBICON MINERALS CORPORATION
George Ogilvie, P.Eng.
President, CEO, and Director

Table 5: Further Details on Geological Modelling and High-Grade Treatment Strategy

Top-Cut Values for Zones 1, 2, 3, and 4:  

CV for Zones 1, 2, 3, and 4:

Table 6: Classified 2018 Mineral Resources by Underground Level¹¹

Cautionary Statement regarding Forward-Looking Statements and other Cautionary Notes

This news release contains statements that constitute "forward-looking statements" and "forward looking information" (collectively, "forward-looking statements") within the meaning of applicable Canadian and United States securities legislation. Generally, these forward-looking statements can be identified by the use of forward-looking terminology such as "believes", "intends", "may", "will", "should", "plans", "anticipates", "potential", "expects", "estimates", "forecasts", "budget", "likely", "goal" and similar expressions or statements that certain actions, events or results may or may not be achieved or occur in the future. In some cases, forward-looking information may be stated in the present tense, such as in respect of current matters that may be continuing, or that may have a future impact or effect. Forward-looking statements reflect our current expectations and assumptions, and are subject to a number of known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any anticipated future results, performance or achievements expressed or implied by the forward-looking statements. Forward-looking statements include, but are not limited to statements regarding the anticipated timing of the filing of the NI 43-101 Technical Report, observations from the 2018 infill drilling and underground development samples from test mining, impact of the data from the 5,000 m of drilling completed in the fourth quarter of 2017 and activities from the 2018 Exploration Program on the 2018 Mineral Resource Estimate, the potential advancement of the Phoenix Gold Project to a viable commercial operation, the potential value of the Company's tax loss pools, the potential to improve the quantities and classification of the 2018 Mineral Resource Estimate, the impact of the new 2018 geological model and information on the Company's understanding of the F2 Gold Deposit and evaluation of mining methods for the Phoenix Gold Project, the additional exploration work required to further improve and reconcile the geological model for the F2 Gold Deposit, the anticipated timing of the reactivation of the Phoenix Gold Project's mill, the further steps necessary to potentially improve upon the 2018 Mineral Resource Estimates, including targeted infill and step-out drilling to potentially convert Inferred Resources to Indicated Resources, using the results from the bulk sampling program for reconciliation and validation purposes, the evaluation of the McFinley Deposit and other close proximity targets for potential inclusion in a future Mineral Resources Estimate, and follow-up drilling of the F2 Gold Deposit at depth and along strike.

Forward-looking statements are based on the opinions and estimates of management as of the date such statements are made and represent management's best judgment based on facts and assumptions that management considers reasonable. If such opinions and estimates prove to be incorrect, actual and future results may be materially different than expressed in the forward-looking statements.

Forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of Rubicon to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. Such factors include, among others: possible variations in mineralization, grade or recovery or throughput rates; uncertainty of mineral resources, inability to realize exploration potential, mineral grades and mineral recovery estimates; actual results of current exploration activities; actual results of reclamation activities; uncertainty of future operations, delays in completion of exploration plans for any reason including insufficient capital, delays in permitting, and labour issues; conclusions of future economic or geological evaluations; changes in project parameters as plans continue to be refined; failure of equipment or processes to operate as anticipated; accidents and other risks of the mining industry; delays and other risks related to operations; timing and receipt of regulatory approvals; the ability of Rubicon and other relevant parties to satisfy regulatory requirements; the ability of Rubicon to comply with its obligations under material agreements including financing agreements; the availability of financing for proposed programs and working capital requirements on reasonable terms; the ability of third-party service providers to deliver services on reasonable terms and in a timely manner; risks associated with the ability to retain key executives and key operating personnel; cost of environmental expenditures and potential environmental liabilities; dissatisfaction or disputes with local communities or First Nations or Aboriginal Communities; failure of plant, equipment or processes to operate as anticipated; market conditions and general business, economic, competitive, political and social conditions; our ability to generate sufficient cash flow from operations or obtain adequate financing to fund our capital expenditures and working capital needs and meet our other obligations; the volatility of our stock price, and the ability of our common stock to remain listed and traded on the TSX.

Forward-looking statements contained herein are made as of the date of this news release and Rubicon disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or results or otherwise, except as required by applicable securities laws. Readers are advised to carefully review and consider the risk factors identified in the Company's annual information form dated March 22, 2018 under the heading "Risk Factors" and in other continuous disclosure documents of the Company filed at www.sedar.com for a discussion of the factors that could cause Rubicon's actual results, performance and achievements to be materially different from any anticipated future results, performance or achievements expressed or implied by the forward-looking statements. Readers are further cautioned that the foregoing list of assumptions and risk factors is not exhaustive and it is recommended that prospective investors consult the more complete discussion of Rubicon's business, financial condition and prospects that is included in this news release. The forward-looking statements contained herein are expressly qualified by this cautionary statement.

Cautionary Note to U.S. Readers Regarding Estimates of Measured, Indicated and Inferred Resources

This news release uses the terms "Measured" and "Indicated" Mineral Resources and "Inferred" Mineral Resources. The Company advises U.S. investors that while these terms are recognized and required by Canadian securities administrators, they are not recognized by the SEC. The estimation of "Measured" and "Indicated" Mineral Resources involves greater uncertainty as to their existence and economic feasibility than the estimation of Proven and Probable Reserves. The estimation of "Inferred" resources involves far greater uncertainty as to their existence and economic viability than the estimation of other categories of resources. It cannot be assumed that all or any part of a "Measured", "Inferred" or "Indicated" mineral resource will ever be upgraded to a higher category. 

Under Canadian rules, estimates of "inferred mineral resources" may not form the basis of feasibility studies, pre-feasibility studies or other economic studies, except in prescribed cases, such as in a preliminary economic assessment under certain circumstances. The SEC normally only permits issuers to report mineralization that does not constitute "reserves" as in-place tonnage and grade without reference to unit measures. Under U.S. standards, mineralization may not be classified as a "reserve" unless the determination has been made that the mineralization could be economically and legally produced or extracted at the time the reserve determination is made. U.S. investors are cautioned not to assume that any part or all of a "measured", "indicated" or "inferred" mineral resource exists or is economically or legally mineable. Information concerning descriptions of mineralization and resources contained herein may not be comparable to information made public by U.S. companies subject to the reporting and disclosure requirements of the SEC.

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