Sirius Minerals Regulatory News (SXX)

10 April 2013

SM11B Preliminary Coring Results

§ Intersection from the deflection SM11B successfully cored through the shelf seam of polyhalite at mine site

§ 58 metres (true thickness) of 88% polyhalite intersected within a total length of 72.4 metres

§ The intersection confirms good correlation between the three intersections from SM11, 11A and 11B

§ SM11B will provide additional input into the upgraded resource report to be completed in early May

The Directors of Sirius Minerals Plc (AIM: SXX, OTCQX: SRUXY) ("Sirius" or the "Company") are pleased to announce the completion of coring of the deflection SM11B (the mine site) at the York Potash Project.

Chris Fraser, Managing Director and CEO of Sirius said:

"This additional deflection has given us further information to improve our confidence in the geological model and early mine planning and these preliminary results provide further confirmation of the volume, quality and consistency of the York Potash polyhalite orebody."

Drilling of SM11B commenced on 22 March 2013 following the completion of the first deflection SM11A. Coring of the Fordon Evaporites commenced on 31 March 2013 from 1,445m below rotary table (bRT) down to 1,598mbRT. Polyhalite was intersected between 1,511.05m and 1587.86mbRT, totalling 72.4 metres (true thickness) at 75% polyhalite (including three bands of anhydritic gangue).

The upper part of the seam is consistent with the intersections at SM11 and SM11A and is in three high grade polyhalite bands (See Table). The thickest is 22m (true thickness) at 84.7% polyhalite correlating with a similar band in SM11 and SM11A. The lower part of the seam, not encountered at SM11 and SM11A, suggests a thickening and enrichment of the seam in a northerly direction. There was 100% core recovery from SM11B.

The preliminary results show a strong correlation between the upper section in SM11B and the findings of SM11 and SM11A, confirming the continuity of the orebody over mining distances which SRK expects will enable the upgrading of a significant portion of the current Inferred Resource to the Indicated Resource category. This will occur following the receipt of chemical analysis of the SM11 core which is expected at the end of April with the upgraded resource estimate expected to be completed at the beginning of May.

Drilling of the North Shaft Pilot Hole at the Doves Nest site will commence in 2 weeks and is anticipated to bring the York Potash drilling programme to a close.

Summary of Preliminary Results - SM11B (Collar: 489320 E, 505337 N; Ground Level 203.1m AOD)

Notes:

1. Rotary table is 4.99 m above ground level

2. Quoted grades and thicknesses are based solely on visual inspection of the core and geological interpretation of the Schlumberger spectral wireline gamma log, assuming that the potassium is present entirely as polyhalite. Assays are required to confirm the thickness and the polyhalite grades.

3. Borehole is deviated. Correction to seam thicknesses has been made based on apparent dip.

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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 the geological model 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.