July 11, 2011

Progress Update on Tongo Kimberlite Dyke Project in Sierra Leone

11 July 2011

AIM: STEL

Stellar Diamonds plc

(“Stellar” or the “Company”)

Progress Update on Tongo Kimberlite Dyke Project in Sierra Leone

Stellar Diamonds plc, the London listed (AIM: STEL) diamond mining and exploration company focused on West Africa provides an operational update on the Company’s Tongo Dyke project located in eastern Sierra Leone.

Highlights:

  • 639 carats of diamonds exported and valued at an average price of $191 per carat
  • 752 carats from 687 dry tonnes for undiluted grade of 109.5 carats per hundred tonnes (‘cpht’)
  • Potential in-situ kimberlite value of $209 per tonne
  • 6,000m drill programme scheduled to commence in August

Chief Executive Karl Smithson commented:

“The valuation of the first parcel of diamonds exported from Tongo is excellent at $191 per carat. Considering that there were no large stones in this parcel this bodes well for any future run of mine diamond values. The average grade of the kimberlite from the bulk sampling to date is over 109cpht which suggests a potential in-situ value of the kimberlite ore body of $209 per tonne, which would make Tongo one of the highest value kimberlites globally on a per tonne of rock basis. With over 80% of the phase-1 surface bulk sampling programme completed, a 6,000m drilling programme will be commencing in August with the objective of defining an initial inferred resource on Dyke 1 to a depth of at least 200m. I look forward to providing further updates as the programme progresses.”

Bulk Sampling and Processing

Bulk sampling of the 2.5km long Dyke 1 kimberlite has continued to yield high grades. Some 1,700t of the planned 2,000t bulk sample has been collected from a 70m long trench that in parts has reached 20m depth. Processing of 1,091t of this material through Stellar’s on-site 5tph DMS plant has yielded 752 carats for a diluted grade of 69cpht. The in-situ grade of the kimberlite, calculated by removing the effects of dilution is calculated as 109.5cpht.

Diamond Valuation

The first diamond parcel recently exported to Antwerp weighed 639 carats. This parcel comprised predominantly gem quality stones and although there were no large or special stones present the goods achieved a high valuation of $191 per carat. This would suggest that the in-situ value of the Tongo kimberlite rock is up to $209 per tonne. The diamonds will be sold via Stellar’s exclusive marketing agent Natural Diamonds Corporation, along with other production goods from the Company’s Mandala project, in due course.

Resource Definition Programme

The ongoing evaluation programme at Tongo will entail completion of the existing 2,000t bulk sample and the collection and processing of further surface bulk samples along the 2.5km strike length of the Dyke-1 kimberlite. A drilling programme is expected to commence in August. The planned 6,000m drilling programme will entail testing of the Dyke along its strike length at 50m, 100m and 200m depth, with the objective of defining an initial inferred resource estimate.

About Stellar Diamonds plc

Stellar is a London (AIM: STEL) listed diamond mining and exploration company focussed on West Africa. Stellar owns a 100% interest in four high-grade kimberlite projects. In Guinea resource definition drilling is continuing on the diamondiferous Droujba kimberlite pipe and bulk sampling is underway on the high grade Bouro kimberlite dyke which is adjacent to the Company’s Mandala alluvial diamond mine. In Sierra Leone at Tongo a bulk sampling programme is ongoing on the high grade Dyke 1 and bulk sampling is planned on the Lion 5 dyke at the Kono kimberlite project.

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

Gavin Burnell, Edward Hutton

Charles Vaughan (Sales) Tel: +44 (0) 20 7796 8800

Daniel Stewart & Company plc

Martin Lampshire, Oliver Rigby Tel: +44 (0) 20 7776 6550

Pelham Bell Pottinger

Charles Vivian / James MacFarlane Tel: +44 (0) 20 7861 3232