September 11, 2012

Completion of Resource Expansion Drilling at Tongo Kimberlite Project, Sierra Leone

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11 September 2012

AIM: STEL

Stellar Diamonds plc

(“Stellar” or the “Company”)

Completion of Resource Expansion Drilling at Tongo Kimberlite Project, Sierra Leone

Stellar Diamonds plc, the London listed (AIM: STEL) diamond development company focused on West Africa, is pleased to announce the completion of its resource expansion drill programme at its Tongo Dyke-1 kimberlite diamond project in eastern Sierra Leone.

Highlights:

  • 11 drill holes totaling 2,929m have extended strike to 2.3km and depth to over 300m
  • Deepest intersection of 357m vertical from surface with the dyke remaining open at depth
  • Drill core has been sent for microdiamond analysis to establish grade continuity with depth
  • CAE Mining Africa currently preparing an updated independent resource statement
  • Current resource of 660,000cts at average grade of 120cpht and diamond value of $248/ct

Chief Executive Karl Smithson commented:

“The resource expansion drill programme has been successfully completed ahead of schedule. Based on a comparison with operating kimberlite dyke mines in South Africa, which are mined to below 700m from surface, Dyke 1 is expected to have further significant depth potential beyond our deepest drill intersection to date of 357 vertical meters. Diamond analysis and resource modelling incorporating these results is underway and we are on track to deliver an updated resource statement in October.

“As announced on the 31st July 2012 the Tongo licence was renewed by the Ministry of Mines in Sierra Leone for three years. This provides us with the confidence to embark upon the next stage of the project development to confirm the long-term economics of the Tongo project. This pre-feasibility study, which will include underground trial mining, will determine the likely run of mine grades, diamond size distribution, recoveries and mining dilution levels. I look forward to providing further updates as we progress over the coming month.”

“In the meantime we continue to progress our discussions with the Government of Sierra Leone in respect of the dispute over the renewal of the Company’s Kono exploration licences.”

Resource Drilling

Phase-2 drilling was completed over the previously untested eastern extension of Dyke 1 and to drill the resource from 200m to 300m depth from surface. Eleven core holes were drilled totaling 2,929 metres and all holes intersected the kimberlite dyke. The deepest intersection of kimberlite was measured at 357.4 metres from surface and the dyke remains open at depth. Overall, Phase-1 and 2 drilling comprised 32 holes for 6,977 metres at 200m intervals along a strike of 2,300 metres.

Updated Tongo Resource Modelling

On 26th March 2012, the company announced the results of the independent maiden resource report completed by CAE Mining Africa. This calculated an inferred resource for Tongo of 660,000 carats at a grade of 120cpht, with a modeled diamond value of between $225 and $270 per carat (all at a +1mm cut-off).

CAE Mining Africa is currently remodeling the Tongo Dyke 1 resource to incorporate these drilling results. With the strike length having been extended to 2.3km and the depth to 300m, and over 350m in one place, we anticipate an increase in the JORC compliant inferred resource tonnage. In addition, once the microdiamond results are received these will be modeled along with the previous bulk sampling and microdiamond data to determine whether the current resource grade of 120cpht can be applied to the newly drilled dyke extensions.

In accordance with the AIM Rules for Companies, the information in this announcement has been reviewed by Karl Smithson, Chief Executive of Stellar, a qualified geologist and Fellow of the Institute of Materials, Metals, Mining, with 23 years’ experience.

About Stellar Diamonds plc

Stellar is a London (AIM: STEL) listed West African focussed diamond mining and exploration company which is advancing the Droujba kimberlite pipe in Guinea and the Tongo kimberlite dyke project in Sierra Leone, which combined have a JORC Compliant, inferred diamond resource of 3.1 million carats. The Company recently announced a dispute with the Ministry of Mines in Sierra Leone over its two Kono licences.

For further information please contact the following or visit the Company’s website at www.stellar-diamonds.com.

Stellar Diamonds plc

Karl Smithson,Chief ExecutiveTel: +44 (0) 20 7257 2930

Northland Capital Partners Limited

(Nominated Advisor and Broker)

Gavin Burnell, Edward Hutton Tel: +44 (0) 20 7796 8800

Daniel Stewart & Company plc

(Co-Broker)

Martin Lampshire, Antony Legge Tel: +44 (0) 20 7776 6550

Pelham Bell Pottinger

James MacFarlane, Joanna Boon Tel: +44 (0) 20 7861 3232