Nautilus Upgrades and Increases CCZ Mineral Resource to over 685 Million Tonnes

TORONTO, ONTARIO--(Marketwired - May 26, 2016) - Nautilus Minerals Inc. (TSX:NUS)(OTCQX:NUSMF)(OTC:NUSMF Nasdaq Intl Designation) (the "Company" or "Nautilus") announces its wholly owned subsidiary, Tonga Offshore Mining Limited ("TOML"), has upgraded its Mineral Resource estimate for its polymetallic nodule project to include portions in the Inferred, Indicated and Measured categories. This follows on from the successful completion of exploration campaigns in the Clarion-Clipperton Fracture Zone ("CCZ") in the Central Pacific in 2013 and late 2015.

Nautilus' CEO Mike Johnston commented, "It is exciting to announce this increase in the CCZ project's inferred mineral resource base from 410 Mt (wet) to 685 Mt (wet) as well the upgrade of an additional 68 Mt (wet) into the indicated category and 2.6 Mt into the measured category".

The Mineral Resource includes portions in the Inferred, Indicated and Measured categories and has been reported in the table below. The Mineral Resource estimate at an abundance cut-off of 6 wet kg/m² is the selected base case scenario considering a non-selective bulk mining operation. Mr Mathew Nimmo, independent Qualified Person ("QP") for the project, has assessed the available information regarding mining and processing of the polymetallic nodules and concluded that there are reasonable prospects for economic extraction. The effective date for the estimate is 30 March 2016 (being the date when the QP received the nodule sample data from TOML).

Mineral Resource Estimate for TOML Areas A-F within the Clarion-Clipperton Fracture Zone

NOTE: *Abundance cut-off of 6 wet kg/m2 used. As the nodules effectively form a single layer on the seafloor, "abundance" (kg/m²) is used to define the mineral resource tonnage. Variations in totals are due to rounding of individual values Mn, Ni, Cu and Co assays on samples dried at 105° C. Moisture content of nodules is estimated at 29% (free water removed after drying at 105°C).

Changes to the Mineral Resource with changes in abundance cut-off are shown below.

http://media3.marketwire.com/docs/1056509.jpg

Nautilus CEO Mike Johnston also noted, "Our updated mineral resource for the CCZ highlights again the significant potential of seafloor resources. Technological advances in mining, oil & gas and maritime technologies over the last 20 years now mean there are reasonable prospects for economic extraction of these massive mineralized systems. At Nautilus, we are both excited and privileged to be leading the development of this significant, currently untapped potential, first with our high grade Solwara 1 Seafloor Massive Sulphide ("SMS") Project, and other SMS systems in the South West Pacific, and now with this updated polymetallic nodule mineral resource in the CCZ."

Mr. Matthew Nimmo, as independent QP, has prepared the technical information that forms the basis for this press release. He has completed this work on behalf of TOML and his work has been independently reviewed by AMC Consultants Pty Ltd. The results set out in this press release will be reported in detail in a Technical Report prepared in accordance with National Instrument 43-101 Standards of Disclosure for Mineral Projects ("NI 43-101"), and submitted on SEDAR within the next 45 days.

Link to map:

http://www.nautilusminerals.com//irm/showmedia.aspx?MediaId=53

Basis of the Mineral Resource Estimate:

The QP for Mineral Resource estimates is Mr Matthew Nimmo. Mr Nimmo is a Member of the Australian Institute of Geoscientists, an independent Consulting Geologist, and fulfils the requirements to be a "qualified person" for the purposes of NI 43-101.

A summary of technical items of interest includes:

Tenure

• All resources are held by TOML, a wholly 100% owned subsidiary of Nautilus. TOML is registered in the Kingdom of Tonga and is subject to all applicable Tongan mining and civil laws and Tongan taxes and royalties.
• The resource falls within the six areas within the Exploration Area granted to TOML, which covers the exploration for polymetallic nodules and formalises the rights of TOML to apply for a "contract for exploitation".

Exploration

• Historic samples were collected by "pioneer contractors" prior to TOML acquiring the property, (Japanese, French, and Russian research organisations), and provided to TOML and the QP by the International Seabed Authority.
• Box-core and photo-profile data were collected by TOML during its 2015 cruise.
• Box-core sampling: nodules were separated from the mud, washed and weighed using a motion compensating scale. The nodules were then laid out on a grid and photographed and then air dried for 30 to 90 minutes. Reference and duplicate samples were selected and all samples placed into plastic bags and then put into drums. The drums were sealed with tamper-proof tape.
• The sample chain of custody and sample security was maintained. There was no evidence of tampering of the samples.
• Nodule abundance was determined from box-core using the weight of the nodules divided by the area of the box-core used. Additional nodule abundance observations were derived from 1 in every 100th photo from the photo-profile lines using the manual long-axis estimation method. The long-axis estimation method involves measuring every nodule long-axis within the photo and then using this in the equation derived from Felix, D. 1980 "Some problems in making nodule abundance estimates from sea floor photographs" Marine Mining, Volume 2, Number 3. The parameters in the equation were calibrated from box-core abundance and the sea-floor photos at the same location as the box-core.

Assaying

• Assays were performed at ALS laboratory (Brisbane), and Jacobs University in Bremen, Germany.
• Additional duplicate samples were selected at the ALS laboratory by TOML during sub-sampling prior to submission to ALS.
• ALS used their chromite/manganese ore fused disk XRF method to analyse elements including Mn, Ni, Cu and Co. They also used high grade four acid ICP-AES for selected samples.
• Jacobs used 0.5M HNO₃ ICP-MS and 0.5M HNO₃ ICP-MS to analyse selected samples.

Quality control

• There is no duplicate or QAQC laboratory data available for the historic sample results.
• There were six groups that sampled the CCZ deposit over various parts using different sampling and assaying methods. Comparison of the data between each of the groups shows that the different sampling achieved similar results over vast areas.
• TOML sub-sampled the box-core samples and collected a random set of 25 duplicate samples for assay by ALS. Comparison of the box-core duplicate sub-samples show no issues with sub-sampling or assaying.
• TOML also submitted 15 duplicate samples to Jacobs laboratory. Comparison between Jacobs and ALS show good agreement for Ni and Co while the Jacobs analyses for Mn show a slight bias low and a slight bias high for Cu.
• Both ALS and Jacobs also analysed internal standards (certified reference material), blanks and duplicates. All analyzed results were within acceptable limits.

Resource Estimation

• Polymetallic nodules occur on the surface of the seafloor at varying abundance across the CCZ.
• Grades were estimated from sample assays using ordinary block kriging.
• Based on the sampling process it was conservatively assumed that the weights in the abundance measurements reported/collected by pioneer contractors were wet but there was some uncertainty as it was not clearly specified by each of the pioneer contractors who collected the data or the ISA who supplied it.
• Based on the reported sample analysis processes, the metal grades were reported on a dry weight basis.
• Estimate of tonnage was based on area and nodule abundance (wet kg/m²). Area was used as there was no effective sampling below the immediate seafloor and mining is only expected to recover nodules from the top 10 cm.
• Abundance was estimated using free fall grab ("FFG") and box core samples, supplemented by estimates derived from photo profiling. Calculation of abundance from photo profiling using nodule long axis follows a previously published procedure, confirmed by laboratory measurements by TOML.
• Estimate of Inferred Mineral Resource abundance is likely to be biased low as most of the historic samples including FFG samples, were within the Inferred Mineral Resource area. FFG samples typically underestimate the abundance of nodules. Correction factors to adjust the likely nodule abundance bias have not been applied.
• Quantitative kriging neighbourhood analysis was performed to check selected estimation parameters.

Mineral Resource Uncertainty

• The highest uncertainty is in estimating nodule abundance due to the nature of the spatial distribution of nodules. However, the photo profile lines demonstrate the continuity in nodule abundance between sample locations and confirm the range of spatial continuity (autocorrelation). The variogram range determined from photo profile percent nodule coverage is consistent with the range determined from the wider spaced samples used in estimating the Mineral Resource. Multibeam backscatter survey results cover the entire area in 30 - 60 m resolution and were used to aid in domaining areas with nodules from areas with very low or no nodules.
• Classification of the Mineral Resource into Measured, Indicated and Inferred categories, in accordance with Canadian Institute of Mining, Metallurgy and Petroleum ("CIM") definitions, considered: the nodule sample quality, uncertainty in the nodule sample abundance and grades, continuity of nodule abundance and grade and scale of the deposit.
• Inferred Mineral Resource classification was based on sampling by pioneer contractors on a nominal spacing of 20 km, the variation and uncertainty in the sample quality, and the likely presence of short range variation to nodule abundance.
• Indicated Mineral Resource classification was based on box core sampling by TOML on a nominal spacing of approximately 7 km by 7 km (including photo profiling in some cases at 7 km by 3 km), supplemented by sampling by pioneer contractors.
• Measured Mineral Resource classification was based on box core sampling by TOML on a nominal spacing of approximately 7 km by 7 km plus photo-profiling on a nominal spacing of 3.5 km by 3.0 km, supplemented by sampling by pioneer contractors.

Development

• No development of deep sea resources has been attempted or demonstrated other than some historical trial mining.
• In the considered opinion of the QP, the Mineral Resource estimate meets the requirement of reasonable prospects for economic extraction. Particular factors of note are:
  • Seabed and sea conditions in the TOML Exploration Area are not materially different from other parts of the CCZ
  • Nodules have been successfully extracted in trials in the past and technological advances are likely to make the next attempts much more efficient; currently there are twelve other parties considering development
  • While TOML and Nautilus have not published any economic assessment for mining seafloor nodules in the CCZ, others have and they consider cut-off values in line with those listed in Table 1.

This Mineral Resource estimate is based upon and accurately reflects data compiled or supervised by Mr Matthew Nimmo, an independent Consulting Geologist, who is a Member of the Australian Institute of Geoscientists. Mr Nimmo has sufficient experience that is relevant to the style of mineralisation and the type of deposit under consideration and to the activity which he has undertaken to qualify as a Competent Person as defined in the 2012 edition of the 'Australasian Code for the Reporting of Exploration Results, Mineral Resources and Ore Reserves' and as a Qualified Person under NI 43-101.

For more information please refer to www.nautilusminerals.com.

Neither the TSX nor the OTCQX accepts responsibility for the adequacy or accuracy of this press release.

Certain of the statements made in this news release may contain forward-looking statements within the meaning of the United States Securities Exchange Act of 1934 and forward-looking information within the meaning of applicable Canadian securities law. Forward-looking statements and forward-looking information include, but are not limited to statements or information with respect to the potential commercial extraction of seafloor resources in the CCZ. We have made numerous assumptions about the material forward-looking statements and information contained herein. Please refer to the Company's most recently filed Annual Information Form in respect of material assumptions and risks relevant to forward looking information. With respect to the CCZ, the "Exploration, Development and Operating Risks" section of the AIF should be read with the particular attributes of the CCZ, versus the Company's Bismarck Sea prospects, in mind. These include the fact that the ocean floor in the CCZ is at much greater depth, the fact that the CCZ is in the middle of the Pacific Ocean and the fact that the Company's plans for developing the CCZ are at a much earlier stage than its plans in respect of its Solwara 1 project. Even though our management believes the assumptions made and the expectations represented by such statements or information are reasonable, there can be no assurance that the forward-looking statement or information will prove to be accurate. Forward-looking statements and information by their nature involve known and unknown risks, uncertainties and other factors which may cause the actual results to be materially different from any future results expressed or implied by such forward-looking statements or information.

Such risks, uncertainties and other factors include, among others as described in the most recently filed Annual Information Form, the risk that the amount of metals contained in the Company's deposits may differ from estimates of resources, the risk that any permits required for development of the CCZ will not be available to the Company, risks associated with financing and executing the required work programs and associated studies, other risks associated with metallurgical properties of the resource, environmental studies, people retention, technology development, intellectual property, logistical support in the CCZ, political interference (from both within and outside the International Seabed Authority), excessive and/or unwarranted non-government organisation attention and/or misinformation campaigns, and risks associated with maintaining the Company's TOML sponsorship. Should one or more of these risks, uncertainties or other factors materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those described in forward-looking statements and information. Although we have attempted to identify factors that would cause actual results to differ materially from those described in forward-looking statements and information, there may be other factors that cause actual results, performances, achievements or events to not be as anticipated, estimated or intended. Also, many of the factors are beyond our control. Accordingly you should not place undue reliance on forward-looking statements or information. Except as required by law, we do not expect to update forward-looking statements and information as conditions change and you are referred to the full discussion of the Company's business contained in the Company's reports filed with the securities regulatory authorities in Canada.

About Nautilus Minerals Inc. Nautilus is the first company to explore the ocean floor for polymetallic seafloor massive sulphide deposits. Nautilus was granted the first mining lease for such deposits at the prospect known as Solwara 1, in the territorial waters of Papua New Guinea, where it is aiming to produce copper, gold and silver. The Company has also been granted its environmental permit for this site.

Nautilus also holds highly prospective exploration acreage in the western Pacific (granted and under application), as well as in international waters in the Central Pacific.

A Canadian registered company, Nautilus is listed on the (TSX:NUS) stock exchange and trades on the (OTCQX:NUSMF), and is also a member of the Nasdaq International Designation program. Its corporate office is in Brisbane, Australia. Its major shareholders include MB Holding Company LLC, an Oman based group with interests in mining, oil & gas, which holds a 27% interest and Metalloinvest, the largest iron ore producer in Europe and the CIS, which has a 15% holding (each on a non-diluted basis, excluding loan shares outstanding under the Company's share loan plan).

Contact

Investor Relations
Nautilus Minerals Inc. (Toronto)
investor@nautilusminerals.com
+1 (416) 551 1100
Principal American Liaison
Euro Pacific Capital, Inc.
88 Post Road West, 2nd Floor
Westport, CT 06880
1-203-662-9700 - Attn: Thomas Tan
ttan@europac.net