Sirius Minerals Regulatory News (SXX)

27 OCTOBER 2011

Sirius Minerals Plc

("Sirius" or the "Company")

Preliminary Coring Results

§ 81.8 metres (true thickness) of total potash mineralisation across all three seams with the hole being terminated while still in polyhalite mineralisation;

§ All three potash seams successfully cored;

§ 65 metres of polyhalite (potassium sulphate) mineralisation within the Fordon evaporites including two zones containing a total of a 19 metres (true thickness) of massive higher grade polyhalite;

§ 7.8 metres of the Boulby potassium chloride seam;

§ 9 metres of the Sneaton potassium chloride seam; and

§ ~100% core recovery.

The Directors of Sirius Minerals Plc (AIM: SXX, OTCQX: SRUXY), the globally diversified potash development group, are pleased to announce the completion of coring at its first borehole at the York Potash Project.

Chris Fraser, Managing Director and CEO of Sirius Minerals, said:

"Although preliminary, these are fantastic results for Sirius. The confirmation of all three seams in exceptional thicknesses is a validation of the world-class status of the project. We are all looking forward to the completion of the chemical assays to confirm the grade of these potash zones. Of particular excitement is the 19 metre thickness of massive polyhalite. This compares very favourably to the 5 metre thickness assumption used in the previously announced Exploration Target.

"The first hole we have drilled in the York Potash Project has delivered one of the world's single thickest potash intersections ever reported."

Completion of SM1 Coring

The drilling programme is being conducted with two rigs. The smaller top-hole rig drills the upper part of the hole in preparation for the larger coring rig to come and complete the hole. Drilling of Pasture Beck - SM1 was commenced on 31 July 2011 with a successful inter-mobilisation of the top-hole rig to the second hole in the drilling programme on 2 September 2011. The coring rig was mobilised onto the project following an extensive refurbishment by the drilling contractor PR Marriott Drilling Ltd ("Marriott"). The coring rig reached the commencement of coring depth on 2 October 2011 and commenced the coring of the entire evaporite sequence from 1,162 metres to 1,669 metres below surface.

The key target potash seams were identified by the Sirius geological team and the cores are now undergoing detailed chemical and mineralogical tests. These tests are expected to take approximately four weeks for the results to be finalised. In the interim, Sirius is pleased to provide some preliminary observations and results from this important project milestone.

Based on the geological analysis and visual inspection of the cores Sirius can confirm SM1 successfully intersected all three potash seams, the Sneaton and Boulby potassium chloride seams and the Fordon polyhalite (potassium sulphate) seam. Wireline geophysical logging is now in progress. The thickness and depth of the intersections observed was broadly in-line with the borehole prognosis and confirmed the outstanding multi-layered potash potential of the York Potash Project.

Set out below in a table is a summary of the observations and interpretations to date. These are based on experienced geologists' visual inspection of the cores and hand-held natural gamma detection devices to confirm the presence of potassium. In addition, a small sample of the massive polyhalite material was also assayed to confirm the visual identification. Confirmation of the thickness and the chemical composition of the potassium mineralisation will however only be possible following completion of the full chemical and mineralogical analysis.

Summary Preliminary Results - SM1 (collar: 493587.28 E, 507066.01 N, 134.8m AOD)

Notes:

1. Depth from sea-level shown due to the varying topography of the York Potash drill sites.

2. Thickness based solely on visual and geological interpretation of the key mineralised zones. Full chemical assays are required to confirm the thickness interpretation and the potassium grades of the mineralisation.

3. "Massive polyhalite rock" refers to the visual interpretation of the cores as being apparently high purity polyhalite with no more than 5% visible halite or anhydrite inclusions. Grade however can however only be confirmed with the completion of the full chemical assays.

4. The dip observed in the polyhalite zone was interpreted to be due to the proximity of a fault line. It is believed to be a localised feature and is not representative of the broader project area and the polyhalite mineralisation within.

Interpretation of the Preliminary Results

SM1 is the first new surface potash borehole for almost 35 years in North Yorkshire and is the first ever hole to target the extraordinary polyhalite potential contained within the York Potash Project. It is therefore useful to put these preliminary results into perspective with the significant amount of historical exploration information that has been analysed.

This new hole adds to a very large database of historical exploration and analysis that has been conducted on the York Potash Project. To date, Sirius and its consultants have analysed data of varying degrees of quality from:

§ 81 historical boreholes- 76 onshore and 5 offshore, representing over 124,000 metres of drilling; and

§ 2,419km of historic seismic data lines- offshore 1,392km onshore 1,027km

The amount of time and cost it would take to replicate all of this drilling and seismic data could easily exceed US$150 million and probably would take anywhere from two to five years to complete. It is this massive database of historical information that delivered the JORC Exploration Targets released on 17 January 2011 and also the confidence in the current drilling programme.

On 17 January 2011, Sirius released the following JORC Exploration Targets.

Between 3.3 and 6.0 Billion tonnes of 67% to 94% polyhalite (19% to 27% K2SO4)1 was established for the then contracted area of mineral rights within the York Potash Project.

This estimate was prepared based on a 5 metre "extraction" section from a >10 metre very consistent seam of relatively high purity polyhalite. This is from within the basin wide 10 to 50 metre thick polyhalite sequence intersected by numerous historical drillholes. Allowances have been made for urban areas and known areas of major fault and dyke disturbance. The base of the polyhalite sequence is expected to be in the order of 1,600m to 1,700m depth below the surface.

Between 330 and 400 Million tonnes of 35% to 40% potassium chloride (KCl)1 was established for the then contracted area of mineral rights within the York Potash Project.

This estimate was defined on the basis of similar characteristics from the drillholes already drilled in the area and what has been mined at the near-by Boulby Mine. Allowances have been made for urban areas and major faulting and an average extraction thickness of 3.5 metres.

1. See Competent Persons Note. These estimates of quantity and grade are conceptual in nature and there has been insufficient exploration to define a Mineral Resource on the property and it is uncertain if further exploration will result in discovery of a Mineral Resource on the property reportable to an AIM standard.

The intersections witnessed in SM1 are consistent with the results of the historical holes that Sirius released a summary of on 11 May 2011 as part of an increase in the mineral rights position. These are repeated here for convenience. Five historical boreholes were drilled on the land and Sirius acquired the core data and exploration logs for four of those boreholes, three of which contain assay data.

All three boreholes for which core and assay data has been obtained intersected the Boulby Potash seam, but were not drilled deep enough to intersect the polyhalite seam. Initial findings are shown below.

A fourth borehole, for which no core or assay data are available, intersected 15.5 metres of the Boulby Potash seam from 1,422 metres depth and 24 metres of mineralisation believed to be polyhalite from 1,562 metres depth. The fifth borehole is also believed to have been drilled to a depth sufficient to pass through the polyhalite seam, but no data are currently available.

Drilling Programme Update

As is often the case in complex exploration drilling, Sirius did experience some unexpected delays during the drilling of this first borehole. Each of these delays has however delivered valuable information and lessons to enable a more accurate planning of the future drilling programme and logistical requirements. The delay experienced since the update provided on 13 September 2011 in obtaining the cores was due to some transition issues as the borehole switched from open-hole boring to wireline coring and the team's determination to obtain complete core recovery from a mineralogically complex sequence of soluble salts, with hard rock interbeds. These teething problems were successfully worked through and delivered a very successful ~100% core recovery in this hole. The drilling team has learnt valuable lessons about the local geology from the first hole and are now in a much stronger position to execute the drilling programme with increased efficiency.

The top-hole rig has now completed work on hole 2 at Howlett Hall near Ugglebarnby (SM2) and moved onto hole 3 at Raikes Lane near Sneatonthorpe (SM3), where progress has been extremely good and final casing is underway. SM2 was cased to a depth of 629m and is ready to receive the coring rig which is now in the process of intermobilisation from SM1 to SM2. SM3 is currently at a depth of 672m below surface and has commenced completion of casing. Preparations for hole 4 (Gough - SM4) are nearly complete and the site will be ready to receive the top-hole rig once it has finished at SM3.

With the experience of SM1, Sirius is now considering what changes should be made to this phase of the project definition drilling programme. Due to the variable hardness of some of the mineral zones above the target horizons, the time to complete coring in each hole is now expected to take marginally longer than originally anticipated. Although this will increase the cost of each hole the Company still expects to delineate a substantial resource within the original exploration budget of £10.5 million.

Sirius is also in discussions with its drilling contractor, Marriott, to explore a number of solutions to potentially save time, accelerate progress, and reduce costs of the total programme. The solutions being explored include the potential of incorporating another coring rig into the drilling programme as well as the possibility of including a rig capable of extracting slim-core for in-fill purposes.

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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 and Western Australia).

The Company is additionally progressing ongoing Research and Development initiatives into the secondary uses of salt and potash beds for energy storage and carbon dioxide sequestration.

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 the use of a sponsored ADR facility. Further information on the Company can be found at www.siriusminerals.com.

Competent Person's Statement and Risk Statement

The information in this Stock Exchange Announcement that relates to Mineral Exploration results and

Exploration Targets, 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. The JORC Exploration Target estimates of quantity and grade are

conceptual in nature and there has been insufficient exploration to define a Mineral Resource on the property

and it is uncertain if further exploration will result in discovery of a Mineral Resource on the Property. The

estimates are not a Reserve or Resource statement in accordance with an AIM recognised Standard and should

not therefore be relied upon as such. It should be noted that the Pan European Code of Reporting or PERC

(that IMMM co-wrote) released in December 2008 and JORC are essentially identical on all key aspects relating

to compilation and quoting Exploration Targets.