Robust updates Romang Island manganese resource estimate

By Ruli Setiawan

ASX-listed Robust Resources Limited refers to the announcement regarding its Manganese Resource Estimate made on 13 May 2014 and provides the following additional technical information in relation there to:

? The mineralisation at Lakuwahi is considered to be hydrothermal in type. The mineralisation occurs in a caldera setting. Three styles of mineralisation have been recognized. Breccia ? style containing galena, sphalerite, chalcopyrite, barite, pyrite, gold and silver (and oxidized portions of this type). Exhalative VMS. Laterally extensive horizon containing galena, sphalerite, chalcopyrite barite, pyrite, gold and silver, Manganese Oxide: replacement of limestone.

? HQ and NQ sized diamond drill core. Triple-tube wireline standard equipment. 1 metre, half core samples collected in visually mineralized intervals. 2-metre quarter core samples in visually non-mineralised or weakly mineralised core.

? HQ and NQ sized diamond drill core. Triple-tube wire line standard equipment. Core is oriented where ever possible using the spear technique.

? Delineated mineralisation of the Lakuwahi Manganese Resource is classified as a resource according to the definitions from JORC 2012 Guidelines. Resource classification is based on data quality, drill density, number of informing samples, kriging efficiency, conditional bias slope, average distance to informing samples and deposit consistency (geological continuity). The high confidence in the quality of the data justified the classification of indicated (56%) and inferred (44%) resources; the data quality does not preclude measured resources. The geological continuity has been demonstrated at 40 m grid spacing over the entire strike of manganese resource. The Lakuwahi manganese resource has been classified as Inferred and Indicated based on the following criteria: Inferred Mineral Resource for which tonnage, grade and mineral content can be estimated on the basis of limited geological evidence and sampling. It is inferred from geological evidence (mapping) and limited sample data. Indicated Mineral Resource for which tonnage, grade and quality can be estimated on the basis of a detailed sampling and testing gathered through appropriate techniques from surface samples and drill core sufficient to confirm geological, grade (including quality) continuity between points of observation where data and samples are gathered. Estimation parameters were also key in identifying indicated mineral resources, the area must have approximately a 40m drill spacing, blocks must be informed by a minimum of 12 samples with an average distance of 30m from the estimated block, estimation statistics were also considered, the krige variance and conditional bias slope were required to be dominantly greater than 0.4.

? Whole sample core pulverized to 80% passing 200 mesh. 50g charge fire assay for gold. Wet geochemical or XRF techniques for silver and other metals. Regular assay suite: Au, Ag, As, Sb, Cu, Pb, Zn, Ba and Mn.

? Estimation is undertaken in Surpac. Kriging of 20 x 20 x 10 m blocks, utilising sub blocks down to 5 x 5 x 2.5m for volume definition. Drill hole samples were composited to 1 metre. Experimental variograms were modelled in Supervisor. Downhole variograms provide very low nuggets not replicated in the directional variograms. Variogram model, 0.2 nugget, C1, 0.55; R1, 40 m and C2, 0.43; R2, 65 m. Ansiotropy ratios of 1.625 and 2. Search neighbourhood: min samples 3, max 15, search 65 m, anisotropy orientated bearing 29? plunge -6? and dip of -19?, anisotropic ratios of 1.625 and 2 for semi-major and minor axis. No other variables were considered in this resource estimate. Sufficient additional data is available to estimate key elements to define major and minor smelter feed quality. Major and minor elements were only considered globally. Block size was 20 m x 20 m x 10 m which considers mineralisation orientation and drill pattern. (Approximately half the drill spacing). Sub-blocking of 5 m x 5 m x 2.5 m for volumes approximating potential selective mining unit. Ore loss and dilution for reserve conversion has not been applied. Wireframes were constructed based on surface mapping, and drill hole intercepts greater than at 30% Mn. Wireframes were used to constrain the estimates in 3D space. Informing samples were composited to one metre, no outlier grades were identified (no grade capping). Global mean grades for estimated blocks and drillhole samples compared closely to estimates. Ordinary krige estimates were compared to nearest neighbour and inverse distance estimates, to assess the impact of data clustering semivariograms and sensitivity to estimation method. No reconciliation data is available for Lakuwahi project as no mining has taken place.

? The mineral resource has been reported above 30% Mn as there is a reasonable assumption this will be a Direct Shipping Ore (DSO) due to the natural breaks in the ore body.

? Manganese mineralisation is enriched close to the surface; Robust envisages shallow open pits targeting DSO material. Assumptions are reasonable and average whole rock analysis report that Fe, Si, Al and P levels are suitable for a DSO, further work is recommended to quantify these parameters. This is an indicated and inferred resource and the project is in early stages of development, it is Robust?s intention to obtain further qualification of DSO specification before work on a Feasibility Study commences. MA notes these are reasonable assumptions based on preliminary test work and experience with other Mn projects and should not be regarded as rigorous at this stage of the project. MA notes that the Indonesian government currently has a levy on export of DSO. Initial characterization test work has been conduct ed on the LK Mn that provides direction for further metallurgical test work, e.g. Litho-geochemistry. No specific metallurgical work has been completed on the Lakuwahi manganese resource. This is an indicated and inferred resource and the project is in early stages of development. It is Robust?s intention to conducted further metallurgical test work, using PQ drill core before defining more indicated or measured resources.

Editing by Johannes Simbolon