Project Studies and Drilling Update

19 November 2012

Sirius Minerals Plc

York Potash Project Studies and Drilling Update

·; Project Study Update for the initial production of large-scale granulated Polyhalite to be released in early December 2012 detailing capital and operating costs estimates

·; Concept Study for the production of NPK fertilizers with Polyhalite as the main source of Potassium ("K") to be released concurrently

·; Additional borehole to be drilled near the mine location to provide additional geological information and geotechnical data for detailed shaft design and mine plan. Subject to these results, Sirius expects to release an Indicated Mineral Resource Statement in the first quarter of 2013

·; Significant increase to Inferred Mineral Resource Estimate to 2.2 billion tonnes of 82.4% Polyhalite, announced on 19 November 2012

The Directors of Sirius Minerals Plc (AIM: SXX, OTCQX: SRUXY) ("Sirius" or the "Company"), the globally diversified potash development group, are pleased to provide an update of the York Potash Project studies and exploration programme.

Chris Fraser, Managing Director and CEO of Sirius said:

"This is a natural evolution of the work we continue to do to refine and optimise the York Potash Project to create the simplest, lowest risk and most sustainable long-term development model. Our strategy has evolved to focus on extracting the greatest value from Polyhalite as we understand more from potential customers about this unique multi-nutrient and multi-product ore. 

"We are in the final stages of completing the Project Study Update which will outline a simplified initial project design that would focus on producing large-scale granulated Polyhalite and include a Concept Study for blending Polyhalite to produce NPK fertilizers. This simplified approach would also allow more capital intensive expansions of the development, such as processing to create sulphate of potash ("SOP"), once the project is into cashflow."

Update on project studies

Following an increased understanding of the potential of Polyhalite as a multi-nutrient fertilizer and also as a source of potassium, sulphur, magnesium and calcium for NPK blending, Sirius expects to release the findings of a Project Study Update for the initial production of granulated Polyhalite and a Concept Study for the production of NPK using Polyhalite as the main blending component in early December 2012.

A substantial amount of optimisation analysis and engineering design work has been completed since the release of the Detailed Scoping Study in April and this has culminated in the York Potash Project attaining a level of accuracy on both capital expenditure and operating expenditure of +/- 25% for the areas of shaft, mineral transport, processing and the port facility for granulated Polyhalite.

The Company was targeting to release a Pre-Feasibility Study on granulated Polyhalite at the end of November; which required an Indicated Mineral Resource Statement to reach a +/-25% level of accuracy for the mining section of the study. The preliminary results of SM9 have resulted in the Indicated Mineral Resource Statement being delayed until additional results are obtained from SM11 in Q1 2013. Therefore the Company intends to release a Project Study Update on granulated Polyhalite in early December 2012 with the following levels of capital and operating expenditure accuracy:

1 Upgrade subject to Indicated Mineral Resource Statement

The Company will release a summary of the results of a Concept Study on production of NPK at Teesside to be announced concurrently with the Project Study Update. The NPK Concept Study is being prepared to a level of accuracy capital and operating expenditure of +/- 50%.

Drilling update

The collation of the preliminary results for SM9 with those of the completed boreholes, the legacy boreholes, new 2D seismic and legacy seismic data, resulted in an updated JORC compliant Inferred Mineral Resource Estimate being prepared by SRK Consultants (UK) Ltd ("SRK"). The increased Inferred Mineral Resource Estimate of 2.2 billion tonnes of 82.4% Polyhalite at the York Potash Project was announced on 19 November 2012.

In consultation with SRK, the Company has decided to focus the drilling programme in the vicinity of the proposed mine location to provide the additional intersections and deflections to upgrade a significant portion of the resource. This drilling will also provide geotechnical data for the detailed shaft design and mine plan. Drilling at SM11 is expected to commence in early December 2012 and subject to results being consistent with the geological model, the Company is targeting announcement of an upgrade to an Indicated Mineral Resource Statement during Q1 2013.

SM9 and 9A (Maybeck) preliminary results

SM9 was completed on 25 October 2012 and SM9A on 10 November 2012, both boreholes intersected Shelf Seam polyhalite. In SM9 an upper seam was cored between 1510.28 and 1516.53 m bRTE. A lower seam was cored between 1549.76 and 1565.15 m bRTE, consisting of two layers of relatively high grade polyhalite separated by 8 m of polyhalitic anhydrite. A similar pattern was found in SM9A, with clear continuity between the two holes in terms of seam level, however intersections in 9A were lower grade.

Preliminary results in each borehole interpreted from field wireline logs, uncorrected for dip and unconfirmed by assay, are as detailed in the following table:

NOTE: Figures rounded to first decimal place.

The results from SM9 give an aggregate of 7.3 m @ 82.8% polyhalite for the two layers of the Lower Intersection. A further deflection SM9B is underway to provide additional information which will be analysed in preparation of the Indicated Mineral Resource Statement.

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About Sirius Minerals Plc

Sirius Minerals is a globally diversified potash development company. Its primary focus is to bring on stream major potash mining facilities through the acquisition and development of projects overlying recognised potash deposits. Today it holds properties in the United Kingdom (North Yorkshire), the United States (North Dakota), and Australia (Queensland). Incorporated in 2003, Sirius Minerals' shares are traded on the London Stock Exchange's AIM market. Its shares are also traded in the United States on the OTCQX through a sponsored ADR facility. Further information on the Company can be found at www.siriusminerals.com.

Qualified Persons

The information in this press release that relates to Mineral Resources is based on information compiled under the direction of Dr Mike Armitage C Eng, who is a Member of the Institute of Materials, Minerals and Mining which is a 'Recognised Overseas Professional Organisation' (ROPO) included in a list promulgated by ASX from time to time.

Dr Armitage is a full time employee of SRK and has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he has undertaken to qualify as a Competent Person as defined in the 2004 Edition of the 'Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves' (the JORC Code) and for the purposes of the AIM Rules. Dr Armitage has reviewed this press release and consents to the inclusion in the press release of the matters based on his information in the form and context in which this appears.

The information in this Stock Exchange Announcement that relates to drilling results, together with any related assessments and interpretations, have been verified by and approved for release by Dr Frederick W. Smith FIMMM., CEng, CSci, a qualified geologist and full-time employee of FWS Consultants Limited ("FWS"), Environmental and Geological Consultants. Dr Smith, who is a Fellow of the Institute of Materials, Minerals and Mining (IMMM), has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person for the purposes of the AIM Rules. Dr Smith and FWS consent to the inclusion of the information contained in this announcement and the respective references to them in the form and context in which they appear.

Graham Clarke, Operations Director for Sirius Minerals Plc, who has reviewed this Stock Exchange Announcement, has over 26 years' experience in the potash mining industry. He has a Degree in Mining Engineering from the University of Nottingham, is a Fellow of the Institute of Materials, Minerals and Mining (IMMM) and extensive operational experience gained at Cleveland Potash Limited in the mining of the Boulby Potash seam and the exploration and development of the upper Fordon Polyhalite seam.