Update on Mikei Gold Project

RNS Number : 2467G

Red Rock Resources plc

27 June 2012

 



RED ROCK RESOURCES PLC

Positive metallurgical test results from four Prospects within the Mikei Gold Project, SW Kenya

27 June 2012

Red Rock Resources Plc ("Red Rock or the Company"), the mineral company with an iron ore project in Greenland, a gold Resource in Kenya, a producing gold mine in Colombia and interests in steel feed, uranium and rare earths, is pleased to provide details of metallurgical test work performed recently on representative samples from the Nyanza (NZ), KKM, KKM-West (KW) and Gori Maria (GM) prospects within the Mikei Gold Project, Migori, South West Kenya.

Highlights - Gold Recoveries

The metallurgical test work was carried out at Wardell Armstrong International LLP's (WAI's) laboratories in Cornwall, on 27 composite samples totalling approximately 217.5 kg. These were sampled and submitted by Red Rock under the recommendation and guidance of Holland & Holland mineral processing consultants.

Prospect	No. Composite Samples*	Total Weight (kg)	Au Recovery (%)
NZ	5	19.5	97.4
KKM	5	27.4	83.7
KW	13	151.4	81.5
GM	4	19.25	Ref. table 2**

Table 1 Summary of prospect composites and corresponding gold (Au) recoveries by cyanide leach

Conditions for NZ/KW: 75 microns grind size; 0.5 g/l CN solution; 72 hours leach residence time. Conditions for KKM: 106 microns grind size; 1.0 g/l CN solution; 72 hours leach residence time.

*Each composite sample is made up of several intersections of drill core (ref. appendix 1). A proportion of each composite sample (ranging from 15-60%) was used to make up ONE total deposit composite for which Au recovery values are shown.

**Au recovery for Gori Maria was not tested as a total composite.

Sample ID	Sample Type	Average Au Recovery (%)
GMMT027	Oxide (HG)	93.8
GMMT028	Fresh (HG)	52.3
GMMT029	Oxide (LG)	89.2
GMMT030	Fresh (LG)	56.3

Table 2 Summary of Gori Maria samples and corresponding Au recoveries by cyanide leach

Conditions for GM: 75 microns grind size; 1.0 g/l CN solution; 48 hours leach residence time.

Summary of test work

The test work, which was completed at WAI's facility in Truro-Cornwall UK, involved:

·     Preparation of three prospect composites, namely NZ, KKM and KW. Preparation of 23 drillhole samples for variability testing and four additional composites from Gori Maria consisting of diamond drill (DD) core samples covering a range of Au concentration (i.e. low to high grade) and material types (i.e. oxide and fresh).

·     Grind size and cyanide strength optimisation tests, in addition to cyanide leach parameter tests, were carried out on the KKM sample. The results were subsequently used to determine the optimum test work conditions.

·     Individual drillhole composites cyanide leach tests as well as comparative CIL tests were carried out under the optimum conditions.

The results for all prospects (refer to Appendix 1) come from the recently completed programme of metallurgical leach testing on the oxide and fresh rock components of the mineral resource, indicate good gold recoveries. This supports the potential for using conventional cyanide leaching techniques with gold recoveries in excess of:

-      90% achievable for NZ

-      80% achievable for KKM and KW

-      90% achievable for oxidised GM and 50% achievable for fresh GM

Detailed Discussion

Nyanza (NZ)

The test work programme focused initially on the optimisation of leach conditions based upon testing of the deposit composite which was generated by blending materials from five discrete diamond drill-hole cores. Once complete, the optimised conditions were then applied to a series of variability tests performed separately on samples from each of the drillholes.

Results from testing to investigate the effect of grind size on amount of Au that could be recovered after 48 hours of leaching is summarized in table 3 below.

Grind Size (µm)	Au Recovery (%)
150	75
106	84.3
75	91.1

Table 3 Summary of Grind Size with corresponding Au Recovery

The results also indicated that the Au recovery could be increased further by prolonging the leach periods. An additional 24 hours of leaching resulted in a nominal 6% increase in the total amount of Au recovered.

A comparative CIL test performed using the optimised leach conditions had 94.2% Au recovery when activated carbon was added to the pulp compared to the 97.3% recovered without the addition of activated carbon.

Results of a diagnostic leach test performed on the composite are summarized in table 4.

Form	Au Distribution (%)
Cyanide Recoverable	97.3
In Sulphides	2.0
In Carbonates	0.4
Encapsulated	0.3

Table 4 Summary of Nyanza deposit diagnostic leach test results

The results in the table above indicate that the majority of the gold lost to tailing is contained within sulphide mineralisation.

KKM and KKM-West (KW)

The KKM deposit composite test work initially focussed on optimising leach conditions in addition to variability testwork on individual drillhole composites. The kinetic leach results for the drillhole composites are outlined in Appendix 1.

Results of the diagnostic leach tests to quantify the distribution of Au that remained in the material after the initial cyanide leach tests is outlined below in table 5:

Form	Au Distribution (%)
Cyanide Recoverable	83.7
In Sulphides	11.5
In Carbonates	1.8
Encapsulated	3.0

Table 5 Summary of KKM deposit diagnostic leach test results

The results in the table above indicate that KKM ore is amenable to processing by cyanide leaching techniques with Au recoveries in excess of 80%. The gold lost to tailing is mainly associated with sulphide mineralisation.

CIL tests on potentially carbonaceous material returned Au recoveries in the range of 63.7 to 92.5%.

Initial testing of the KW deposit composite consisted of investigation of effect of grind size on Au recovery and investigating the effect of cyanide concentration on leach recoveries. The results of this test work using 1.0g/l of cyanide are summarised in table 6.

Grind Size (µm)	Au Recovery (%)
150	66.0
106	81.5
75	77.6

Table 6 Summary of Grind Size with corresponding Au Recovery

Following preliminary optimisation of the leach conditions, the leach residue was subjected to the diagnostic leach test to quantify the distribution of Au that remained in the material after the initial cyanide leaches. The results are summarised in table 7.

Form	Au Distribution (%)
Cyanide Recoverable	77.6
In Sulphides	15.5
In Carbonates	2.6
Encapsulated	4.3

Table 7 Summary of KW deposit diagnostic leach test results

The above again indicate the non-leachable gold in the tailing is associated with sulphide mineralisation.

In addition to the cyanide leach tests, a Bond Ball Mill Work Index determination was also undertaken on the KW Prospect composite to quantify the hardness of the material with respect to grinding energy requirements. The Prospect composite attained a Bond Ball Mill Work Index of 20.41kWh/t. This Bond Work Index is extremely high and will require verification during the next phase of testwork.

Gori Maria (GM)

Four composite samples representing high and low grade Au mineralisation from two ore types i.e. oxide and fresh rock, were subjected to a single cyanide leach test performed at a grind size of 80% passing 75µm, using 1.0g/l cyanide solution and a leach time of 48hours.

The results of this test work to determine the amount of recoverable Au (outlined in Appendix 1) shows that it is possible to achieve Au recoveries of up to 93.8% for the oxide resource and up to 56.3% for the fresh rock resource via conventional cyanide leaching technique.

Further test work

Further test work will be undertaken to improve the gold recoveries of the Mikei Gold Project but the above results are considered positive for the definition of economic resources.

Sampling for similar metallurgical test work on the MK prospect is currently underway, and results are expected soon. Historical work from 1990 showed good gold recovery from MK drill core samples (from an unknown location).

Mineral Resource Estimation is underway on the NZ, KW, GM and MK Prospects within the Mikei Gold Project and first results are expected shortly. The KKM Prospect was reported to contain an Indicated and Inferred JORC Resource of 17.8 Mt @ 1.01g/t Au for 577 kOz Au in December 2011.

Appendix 1 Summary of diamond drillhole composites and corresponding Au recovery values

Prospect	Composite Sample ID	Hole ID	Number of Intersections	Au Recovery (%)	Comments
KKM	KKMT001	KKDD024	2	96.6	Oxide; high grade
	KKMT002	KKDD027	7	74.9	Fresh; low grade, carbonaceous
	KKMT003	KKDD027	7	76.2	Fresh; high grade, carbonaceous
	KKMT004	KKDD072	5	60.9	Fresh; low grade
	KKMT005	KKDD077	5	87.5	Fresh; high grade
NZ	NZMT007	NZDD093	8	87.0	Fresh; low grade
	NZMT008	NZDD102	2	99.4	Fresh; high grade
	NZMT009	NZDD103	3	95.8	Fresh; high grade
	NZMT010	NZDD105	3	93.6	Fresh;  low grade
	NZMT011	NZDD106	5	94.9	Oxide; low grade
KW	KWMT013	KWDD032	10	43.4	Fresh; low grade
	KWMT014	KWDD039	1	99.1	Fresh; high grade
	KWMT015	KWDD043	10	94.0	Fresh; high grade
	KWMT016	KWDD051	12	86.9	Fresh; high grade
	KWMT017	KWDD053	3	65.5	Fresh; high grade
	KWMT018	KWDD060	19	81.9	Fresh
	KWMT019	KWDD061	10	87.1	Fresh
	KWMT020	KWDD065	3	96.1	Fresh
	KWMT021	KWDD073	16	90.0	Fresh
	KWMT022	KWDD078	19	83.2	Fresh
	KWMT023	KWDD083	12	86.0	Fresh
	KWMT024	KWDD085	26	72.6	Fresh
	KWMT025	KWDD087	20	79.3	Fresh
GM	GMMT027	GMDD003	4	93.8	Oxide; high grade
	GMMT028	GMDD003	7	52.3	Fresh; high grade
	GMMT029	GMDD007	3	89.2	Oxide; low grade
	GMMT030	GMDD007	4	56.3	Fresh; low grade

Enquiries:

Andrew Bell	020 7402 4580 or 07766 474849	Red Rock Resources plc	Chairman
Sandra Spencer	020 7402 4580 or 07757 660 798	Red Rock Resources plc	Public and Investor Relations
Philip Davies/David Porter	020 7444 0800	Religare Capital Markets	Nominated Adviser
Nick Emerson	01483 413500	Simple Investments Ltd	Broker

 

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