Nautilus Minerals Inc.: Solwara 1 Drilling Program Update

Nautilus Minerals Inc. has successfully completed the majority of the exploration fieldwork for its Solwara 1 project in the territorial waters of Papua New Guinea with 92 holes drilled to date this year within this high-grade copper and precious metal massive sulphide system.

Highlights:

Targets achieved — 92 holes completed in Solwara 1 this year; Open at depth — 40 per cent of all holes end in mineralization; Improved recoveries — 72-per-cent recovery from sulphide intercepts; On track — Solwara 1 preliminary resource and mine model due end of the fourth quarter 2007.

• Targets achieved — 92 holes completed in Solwara 1 this year;
• Open at depth — 40 per cent of all holes end in mineralization;
• Improved recoveries — 72-per-cent recovery from sulphide intercepts;
• On track — Solwara 1 preliminary resource and mine model due end of the fourth quarter 2007.

David Heydon, Nautilus’s chief executive officer, commented: “We are developing a drill-tested geological model for a sea floor massive sulphide system, with preliminary indications (using XRF spectography) suggesting an extensive high-grade system.

“We expect assays over the coming weeks to show the tenor of the orebody system at depth, in addition to the high-grade massive sulphide chimneys/spires — often 10 metres high — that are perched upon it.

“The remote operated vehicle drill (ROV drill) which sits on the sea floor recovering drill cores up to 19 metres in length has gone from an idea, to design, to implementation within a year. This is a significant technical achievement — and bodes well for future exploration and mining activities.

“Nautilus’s exploration at Solwara 1 for the 2007 field season will be completed by late September and laboratory assays will be available in September through October in the lead up to the announcement of a preliminary resource model later this year.

“We are now looking to future campaigns and considering new drills to increase productivity, further improve core recovery and, more importantly, provide the ability to test the systems to greater depth.”

Solwara 1 program

Since drilling commenced on June 14, 2007, at Solwara 1, 92 holes have been completed for a total of 879 metres, with an average core recovery for massive sulphide intercepts of 72 per cent.

This drilling is mostly adjacent to the exposed high-grade sulphide outcrop zones defined by previous surface sampling and mapping.

The evaluation drilling of Solwara 1 is conducted on a nominal 30-metre grid with the aim of collecting sufficient samples for preparation of a mineral resource statement, metallurgical evaluation and mine planning purposes.

As previously advised, Nautilus anticipates releasing a preliminary resource and geological model later this year, and has retained Golder Associates and SRK Consulting to provide independent technical advice in the development of a resource model consistent with 43-101 standards.

SOLWARA 1 — 2007 ROV DRILL — SELECTED INTERCEPTS

Sulphide intersection

Core Cu%

recovery- Intersection hand-

Drill hole Depth in sulphide From To width held

No. (m) (%) (m) (m) (m) XRF(i)

SD065 9.6 73 0.2 8.3 8.1

hole ended

in sulphide 13.8

SD072 15.1 41 1.7 8.2 6.5 12.2

SD116 14.2 69 0.4 13.0 12.6

hole ended

in sulphide 14.0

SD120 6.7 63 0.6 6.7 6.1

hole ended

in sulphide 14.5

SD121 15.6 71 0.6 15.6 14.9

hole ended

in sulphide 8.4

SD123 16.4 85 0.2 6.4 6.2 12.4

(i) The hand-held XRF does not analyze for gold or silver.

Geological sequence

The improved core recovery from this year’s program has revealed a geological sequence that is essentially consistent with land-based volcanogenic massive sulphide deposits like Kidd Creek and Horne. The surface expressions of the system are zones of chimneys up to 20 metres with an average height of about five metres to 10 m surrounded by unconsolidated muddy sediments.

These chimney zones have been sampled at surface with a total of 146 samples reporting an average grade at Solwara 1 of 11.3 per cent copper (Cu), 15.2 grams per tonne gold (Au) and 4.7 per cent zinc (Zn). Underlying the muddy sediments and inferred to be lapping onto the chimneys is a zone of variably consolidated sandy volcaniclastic rock containing large clasts of sulphide, probably derived from fallen sulphide chimneys.

The massive sulphide zone which has been drilled locally to a maximum depth of 19 m (due to limitations of drill rig) is dominated by the minerals pyrite and chalcopyrite and has a characteristic vuggy texture. The main ore zone increases in thickness toward the centre of the ore zone, to in excess of 19 metres. Many drill holes in the central spine region ended in sulphide mineralization and remain open at depth, with 40 per cent of all holes ending in mineralization.

Drilling below the massive sulphide zone shows that it has a transitional contact with a zone of disseminated sulphide in altered volcanic rocks containing variable chalcopyrite mineralization. This footwall zone has not yet been intercepted in the central part of the system, which in many terrestrial deposits has a mineralized Cu stringer zone.

The altered volcanic rocks at the base of the system are underlain in places by fresh unaltered volcanic rocks, particularly around the flanks of the ore zone. These feldspar porphyritic volcanic rocks are vesicular and likely to be andesitic to dacitic in composition.

Metallurgical testwork

Sixteen holes have been drilled to provide a metallurgical sample of 740 kilograms which has been forwarded to Ammtec Ltd. in Perth, Australia, to conduct testwork comprising comminution, mineralogy and bench-scale froth floatation trials. This testwork will provide valuable input to the detailed concentrator plant design and provide concentrate samples for marketing purposes. These holes have also sampled the short-range grade and geological variability.

Geotechnical testing

A geotechnical laboratory has been established aboard the Wave Mercury and an extensive program of geotechnical testwork has been completed on drill core from the current drilling program. In excess of 350 rock strength tests have been completed. UCS strengths in the massive sulphide zone are typically in the range from three megapascals to 35 megapascals and average about 18 megapascals. The compressive strength to tensile strength ratio averages about nine.

Over 600 dry bulk density measurements have been determined using a caliper method and a water displacement method. The results from the two methods are in close agreement. The average dry bulk density of the massive sulphide zone is approximately 3.3 tonnes per cubic metre. The geotechnical testing results are consistent with independent laboratory testwork completed in 2006. Further geotechnical testwork, including triaxial testing under high confining pressures, is planned for later this year.

Solwara 1 ROV drill intercepts

Qualified person

The exploration results reported in this announcement have been compiled under the supervision of Anthony O’Sullivan, chief operating officer of Nautilus. Mr. O’Sullivan is a member of the Australasian Institute of Mining and Metallurgy, has 20 years of experience in mining and exploration geology, and is a qualified person as defined under National Instrument 43-101. He consents to his name being used in this release.

Results of indicative analyses from hand-held XRF unit

Nautilus is using a hand-held Niton XLT 592 X-ray florescence (XRF) instrument on the Wave Mercury to obtain indications of the grade of materials recovered from the sea floor. This system provides indicative information on grade tenor of samples for copper, zinc and lead mineralization but does not measure for many elements including gold and silver. It is unable to provide gold and silver assays.

The instrument used for this application does not provide the accuracy required to report assays. These analyses are the mean of 10-point measurements on unprepared wet surfaces of each of the samples reported. XRF readings are taken at 10-centimetre intervals along the drill core to provide indicative grade data for mineralized intervals. The instrument is not calibrated using certified standards and the samples have not been crushed and prepared to minimize matrix effects which may affect the accuracy of the analysis. However, a comparison of results to date with assay data for surface samples indicates the XRF tool is a reliable method for providing indicative results of the tenor of mineralization and providing data for real-time decisions in the field.

Measurements by hand-held XRF are not assay results and do not measure gold or silver. Samples will be formally assayed by the ALS Group in Brisbane.

Laboratory analysis

More than 1,000 samples have been received by ALS Laboratory Group in Brisbane, Australia. ALS operates quality systems based on international standards ISO/IEC17025:1999 — general requirements for the competence of calibration and testing laboratories — and ISO9001:2000 — quality management systems, requirements.

Sample custodianship

All sampling, sample handling and analysis were completed under the supervision of Nautilus personnel. Sampling was carried out aboard the Wave Mercury whilst at sea. All subsamples were placed into numbered plastic vacuum-sealed bags. The bagged samples were subsequently placed into boxes. The boxes were sealed with uniquely numbered security tags and checked upon arrival to the laboratories. A full electronic chain of custody is maintained whilst the samples are under the care of ALS.

Quality assurance

External certified geochemical reference materials were prepared by Geostats Pty. Ltd., of Perth, Western Australia, with known and statistically tested concentrations of the major base and precious metals. Standards were submitted approximately every 10th sample.

A review of sampling procedures and work processes for collection of samples at sea has been undertaken by Golders Associates with no adverse conclusions.

SOLWARA 1 ROV DRILL INTERCEPTS (HOLES SD065 TO SD 127)

(Nautilus reported drill results for holes SD36 to SD64 in Stockwatch

news July 11, 2007)

Cu%

weighted Recovery

Sulphide average sulphide

Drill hole width (hand-held intercept

No. (m) XRF) (%) Comment

SD065 8.1 13.8 73 hole ended in massive sulphide

SD066 volcanic rock — barren

SD067 3.6 8.9 78 hole ended in massive sulphide

SD068 5.4 6.1 29 hole ended in massive sulphide

SD069 7.6 4.1 86 hole ended in massive sulphide

SD070 mechanical fault — terminate hole

SD071 7.3 3.9 83 hole ended in massive sulphide

SD072 6.5 12.2 41

SD073 volcanic rock — barren

SD074 8.1 4.7 76 hole ended in massive sulphide

SD075 14.1 6.9 47 hole ended in massive sulphide

SD076 7.2 3.7 69 hole ended in massive sulphide

SD077 9.0 2.3 72 hole ended in massive sulphide

SD078 0.3 11.0 100

SD079 6.7 5.9 100 hole ended in massive sulphide

SD080 11.4 12.1 54 hole ended in massive sulphide

SD081 volcanic rock — barren (1.2 m less than 1% Cu)

SD082 volcanic rock — barren

SD083 4.7 2.6 81

SD084 volcanic rock barren

SD085 0.6 3.2 98

SD086 0.3 1.2 93

SD087 3.3 3.7 67

SD088 5.8 9.1 47 hole ended in massive sulphide

SD089 2.6 7.0 91

SD090 6.1 1.9 64

SD091 0.8 2.3 85

SD092 volcanic rock — barren (0.6 m less than 1% Cu)

SD093 3.8 10.3 66

SD094 3.9 2.0 41 hole ended in massive sulphide

SD095 volcanic rock — barren

SD096 volcanic rock — barren

SD097 0.5 1.3 100 hole ended in massive sulphide

SD098 7.9 3.4 53 hole ended in massive sulphide

SD099 7.6 5.9 49 hole ended in massive sulphide

SD100 14.9 5.2 91 hole ended in massive sulphide

SD101 mechanical fault — terminate hole

SD102 mechanical fault — terminate hole

SD103 mechanical fault — terminate hole

SD104 0.6 3.9 100 hole ended in massive sulphide

SD105 5.5 7.5 73 –

SD106 7.9 3.6 75 –

SD107 hole collapse — thick sediments

SD108 hole collapse — thick sediments

SD109 9.6 7.3 93 hole ended in massive sulphide

SD110 0.5 1.2 100 mechanical fault

— terminate hole

SD111 volcanic rock — barren

SD112 16.0 6.7 80 hole ended in massive sulphide

SD113 volcanic rock — barren (minor Zn sulphides)

SD114 1.0 1.4 100 –

SD115 mechanical fault — terminate hole

SD116 12.6 14.0 69 hole ended in massive sulphide

SD117 2.5 6.5 68 hole ended in massive sulphide

SD118 7.4 1.9 26 –

SD119 5.9 7.1 61 –

SD120 6.1 14.5 63 hole ended in massive sulphide

SD121 14.9 8.4 71 hole ended in massive sulphide

SD122 4.2 6.9 41 –

SD123 6.2 12.4 85 –

SD124 3.4 5.4 78 –

SD125 7.4 5.3 73 hole ended in massive sulphide

SD126 5.3 4.6 73 hole ended in massive sulphide

SD127 16.0 3.2 98 hole ended in massive sulphide