Rockwell Diamonds Inc
Monday, October 1st, 2007
Rockwell Diamonds Inc. announces the results of a mineral resource estimate for the Wouterspan alluvial diamond property on the Middle Orange River (â€œMORâ€) in the Northern Cape Province of South Africa. The Wouterspan property held by Rockwell is comprised of Farhom and Okapi farms. Rockwell currently holds a 51% interest in the Wouterspan property.
The indicated and inferred resources estimated for the Farhom and Okapi portions of Wouterspan at March 31, 2007 are 15,814,000 cubic metres (m3) and 20,748,000 m3 respectively, which are shown in the Table below.
Reverse circulation drilling and bulk sampling is on-going on Wouterspan and it is likely that once the next phase of drilling and bulk sampling is complete by the end of 2007 that indicated and inferred resource volumes presented below will show further increases.
Classification, Area, Volume(m3), Grade(carats per 100 m3)
Indicated Farhom 6,144,000 0.63
Okapi 9,670,000 0.63
Total Indicated 15,814,000 0.63
Inferred Farhom 2,895,000 0.63
Okapi 17,853,000 0.63
Total Inferred 20,748,000 0.63
The MOR is a well known area for alluvial diamond production, and in particular the occurrence of large diamonds, which may be over 100 carats in size. The majority of the alluvial diamonds along the MOR are found in two distinct gravel horizons: an upper deflation deposit called the Rooikoppie gravel and the basal Primary gravels. These two horizons are typically separated by a hard layer of calcrete.
The Rooikoppie gravel comprises a diamond-bearing lag deposit created by erosion, winnowing and removal of light components, and enrichment of heavy components including diamonds. This Rooikoppie unit varies in thickness from a few centimetres up to about 2 metres and has an average thickness of about 1 metre. The basal Primary gravel deposits comprise the lower half to one third of the sedimentary sequence and rest directly on bedrock. These Primary gravels comprise a poorly sorted assemblage of large boulders (up to 45 centimetres in diameter at the base of the unit), cobbles and pebbles set in a sandy matrix. The total sedimentary sequence, including calcrete varies from about 8 to 18 metres in thickness.
The thickness and distribution of the alluvial gravel deposits have been investigated through systematic percussion circulation drilling programs. Geological logging and surveying of all boreholes have been undertaken and used in the construction of a 3D geological model, which has itself been used as a guide to the bulk sampling program. Bulk sampling is only way to establish diamond presence and grade of these deposits.
A percussion drilling program conducted in 2005 and 2006 comprising 469 bore holes and 5,589 metres of drilling identified 4,481,000 m3 of Rooikoppie gravel and 43,259,000 m3 of Primary gravel on the Wouterspan property. From March 2005 to January 2006, a total of 513,892 m3 of Primary gravel and 24,013 m3 of Rooikoppie gravel from eleven locations on the Wouterspan property were tested by bulk sampling.
For the period March 2005 to March 31, 2007 some 12,000 carats of diamonds were produced from Wouterspan. In the bulk sampling operations conducted between January 2006 and March 2007, 8,940 carats of diamonds were recovered from a total feed of 1,420,699 m3 of diamond bearing gravel for an average global grade of 0.63 carats per 100 m3. The average diamond value for this period was US$2,250 per carat.
Studies of the MOR deposits have indicated an average density or specific gravity of 2.1 would be used to convert cubic metres to tonnes, which would be the norm for resources reported under NI 43-101. Hence, the total indicated mineral resources would equate to about 33.2 million tonnes and the total inferred mineral resources would be about 43.6 million tonnes.
Indicated and inferred resources have been defined by combining geological observations, drill results, and bulk sampling information on a sectional basis for those areas lying within the drilled and sampled portion of the Wouterspan project. Indicated resources have been estimated for Farhom for areas with a drill grid of 50 metre x 100 metre spacing and for Okapi as 100 metre x 200 metre grid spacing for which grade, diamond size and diamond value (calculated on a weighted average from fourteen monthsâ€™ production) has been extrapolated and interpolated to a maximum of 250 metres from the blocks that were bulk sampled. Inferred resources have been designated for those areas for which the same drill grid spacing applies, but where distances from the bulk sampled blocks are greater than 250 metres; such areas, although showing the same geological consistency in drill samples and pits, are considered to be of lower confidence level in respect of grade and diamond characteristics.