Nautilus Minerals Inc.: Solwara 1 Metallurgical and Mineralogical Results

Nautilus Minerals Inc. has released preliminary results from its first-phase mineralogical and metallurgical investigations of ore from a representative 1.2-tonne drill-core sample recovered during the 2007 drilling campaign at the company’s Solwara 1 project, located in the territorial waters of Papua New Guinea (PNG).

David Heydon, Nautilus’s chief executive officer, said: “The results of the mineralogical program conducted at G&T Metallurgical Services of Canada and the initial phase of metallurgical work carried out by AMMTEC of Australia provide clear evidence that the Solwara 1 material is a ‘simple ore’ that should produce a commercial-grade copper concentrate with low impurity levels and good recovery.”

The mineralogical work was carried out by G&T on composite samples recovered from Solwara 1 during the 2007 drilling campaign, as documented in the resource report completed by Golder and Associates and released on Feb. 1, 2008.

The program was designed to provide data to optimize the flotation process design. The following key points have been concluded from this mineralogical work:

Chalcopyrite is the dominant copper-ore mineral.The gangue is pyrite, barite, anhydrite and minor silicate minerals, all of which are readily separated from chalcopyrite using standard flotation techniques.The majority of the massive sulphide tested is course grained. Grinding tests indicate effective liberation with a likely primary grind size of 80 per cent — 50 microns.The principal impurity element, arsenic, is held almost exclusively in the mineral arsenopyrite. Grinding tests indicate that the arsenopyrite is readily liberated from the chalcopyrite and flotation will produce concentrates with acceptable arsenic contents.The copper concentrates will likely contain significant gold contents and, in some cases, payable levels of silver. Further work into gold and silver deportment is under way.

• Chalcopyrite is the dominant copper-ore mineral.
• The gangue is pyrite, barite, anhydrite and minor silicate minerals, all of which are readily separated from chalcopyrite using standard flotation techniques.
• The majority of the massive sulphide tested is course grained. Grinding tests indicate effective liberation with a likely primary grind size of 80 per cent — 50 microns.
• The principal impurity element, arsenic, is held almost exclusively in the mineral arsenopyrite. Grinding tests indicate that the arsenopyrite is readily liberated from the chalcopyrite and flotation will produce concentrates with acceptable arsenic contents.
• The copper concentrates will likely contain significant gold contents and, in some cases, payable levels of silver. Further work into gold and silver deportment is under way.

MINERALOGICAL COMPOSITION OF SOLWARA 1 ORES

Mineral Deposit composites

Sample 2(1) Sample 3(1)

Chalcopyrite 20.9% 29.2%

Bomite 0.1% 0.3%

Chalcocite/covellite 0.1% 0.1%

Tennantite/tetrahedrite 0.13% 0.17%

Galena 0.1% 0.1%

Sphalerite 0.9% 0.5%

Arsenopyrite 0.44% 0.22%

Pyrite 56.2% 56.7%

Gangue 21.0% 12.7%

Total 100% 100%

(1) Sample described in resource report in Stockwatch on

Feb. 1, 2008.

Metallurgical testwork on the ore samples recovered from Solwara 1 continues at AMMTEC laboratories. Initial results from grindability tests indicate that the ore is soft with expected bondwork indices values in the range of 10 to 12 kilowatt-hours per tonne. Initial flotation testwork which, to date, only extends to a single, cleaner-stage testing, indicates that a commercial-grade concentrate (25 per cent or greater copper) at high recovery can be produced from all major ore types. Further testwork to extend the current single-stage cleaning to three-stage production of a separate pyrite concentrate for gold deportment and optimization of reagent use is under way. This work is expected to be completed by the end of April, 2008.

The metallurgical and mineralogical results reported in this announcement have been compiled under the supervision of Peter Munro, a full-time employee of Mineralurgy Pty. Ltd. and Dr. N.W. (Bill) Johnson, a consultant for Mineralurgy Pty. Ltd. Both are corporate members of the Australasian Institute of Mining and Metallurgy with over 20 years experience in mining and metallurgical process engineering and are deemed to be qualified persons. Both members have consented to their names being used in this release.