Sirius Minerals Regulatory News (SXX)

5 March 2013

SM11 Preliminary Coring Results

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

§ Wireline logging of borehole provides preliminary seam data

§ 26.6 metres (true thickness) of polyhalite has been intersected in two seams which average 87.8% polyhalite and which are separated by 5.7 metres of anhydrite

§ Preliminary results appear to support the geological model created by geological consultants SRK

§ Deflection borehole will provide a second intersection

The Directors of Sirius Minerals Plc (AIM: SXX, OTCQX: SRUXY) ("Sirius" or the "Company"), the globally diversified potash development group, are pleased to announce the completion of coring of the mother hole at SM11 (the mine site) at the York Potash Project.

Drilling at SM11 commenced on 19th December 2012 and coring of the Zechstein Evaporite section commenced on 10th February 2013 from 1259 metres below Rotary Table Elevation (bTRE), down to TD at 1580 metres bRTE. The shelf polyhalite seam was intersected between 1502.82 metres and 1549.45 metres bRTE. Details of the seam, including two anhydritic bands, are given in the table below, based on interpretation of Schlumberger's spectral gamma wireline log. Depths are below rotary table; and the seam thickness is corrected for dip - to give a close approximation to the true thickness. The best section was intersected between 1516.68 metres to 1538.33 metres bRTE, and totals 21.31 metres (true thickness) grading 88.0% polyhalite, within which are two exceptionally high grade sections totalling 17 metres at 92% polyhalite. Core recovery was excellent throughout.

Chris Fraser, Managing Director and CEO of Sirius said:

"This is an extremely encouraging result as this is a sample of the first ore to be mined at the bottom of the shafts and is further confirmation of the high quality nature of this unique multi-nutrient deposit.

"A deflection from this hole is now planned which, if consistent and combined with the assay results from cores recovered, should deliver an upgrade to the resource estimate."

Summary of Preliminary Results - SM11 (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 approximately vertical. Approximate average dip is measured from the core. Wireline logging and gyro survey will determine the actual, true dip.

Although coring of the "mother hole" is complete, work continues on SM11 with additional wireline logging, an off-set seismic survey, and a borehole gyro survey, to be followed by the drilling of a deflection - "SM11A".

This deflection will generate detailed information on lateral continuity of the mineralisation and will provide an additional core of the polyhalite horizon. Once assayed, this information will be imported into the geological model that was been used to estimate the Company's current Inferred Resource and then used to update this.

The SM11 core will be sampled shortly and tests for polyhalite content carried out at the laboratory facilities of the British Geological Survey ("BGS"). Once coring is complete of SM11A these samples will also be sent to the BGS for analysis.

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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 Geol 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.