The phosphate mineralisation at Langey Crossing was first discovered during the mid 1960s. Drilling at the time defined the broad outlines of mineralisation associated with a shallow dipping nodular phosphate horizon in the Langey crossing area on the western bank of the Fitzroy River 60km south west of the port of Derby in the Kimberley Region of Western Australia.
Phosphate is a key component of fertilizer and premium quality rock-phosphate prices have risen some seven times from approximately US$65 per tonne to over US$375 per tonne during 2007/2008. This price increase was primarily driven by demand from China and is closely tied to the demand for Sulphur, the other component of fertilizer manufacture. The primary supplier of Phosphate is Morocco in North Africa.
The Company applied for Exploration Licences over the phosphate occurrence in July 2007. The tenements were recently granted and Heritage surveys have been completed with the Traditional Owners of the land, through the Kimberley Land Council. Exploration will consist of an extensive drilling and sampling program targeting this shallow horizon supported by metallurgical testwork to determine the optimum product grade.
Reconnaissance sampling of the outcropping Phosphate nodules returned average results of 22.5% P2O5 with very consistent assays recorded for all seven samples as shown in the table below.
| Sample | P2O5% | FeO% | Al2O3% | SiO2% |
|---|---|---|---|---|
| R100297 | 23.0 | 3.6 | 3.5 | 31.2 |
| R100298 | 22.2 | 4.7 | 4.4 | 30.2 |
| R100299 | 21.5 | 3.8 | 3.8 | 29.8 |
| R100300 | 23.0 | 3.9 | 3.8 | 29.8 |
| R100301 | 22.1 | 4.7 | 4.5 | 30.0 |
| R100302 | 22.6 | 2.6 | 3.4 | 32.3 |
| R100303 | 23.4 | 4.8 | 4.1 | 28.4 |
The Company completed a reconnaissance drilling and costeaning program during September 2008. Grid based reverse circulation drilling was completed in late October with a total of 151 holes for 2,263m being drilled. The drilling program has delineated the phosphate horizon over some 14 kilometres of strike north and south of the Great Northern Highway. Eight shallow costeans were also dug with a small excavator on the eastern side of the occurrence where the phosphate horizon comes to within one metre of the surface.
The results indicate that a thin horizon of phosphatic nodules is present at the base of the glauconitic Jarlemai Formation over the tested strike length of 14 kilometres. Phosphate grades for the nodular horizon over the 0.5 metre sample interval averaged approximately 4.2% P2O5. The phosphate nodules themselves have an average grade of approximately 21% P2O5, indicating that the target horizon contains about 20% nodules by weight. This calculated average nodule concentration is supported by mapping in the costeans, although there were indications that the nodule horizon is thicker and better developed in the northern part of the area.
The horizon comes to within a metre of the surface on the eastern side and then gently dips to the west for a distance of over one kilometre. The phosphate horizon consists of both scattered and more packed nodules within an approximately two metre thick host glauconitic unit.
Metallurgy and preliminary evaluation
Preliminary flotation tests on the phosphate nodules have produced a concentrate grading 31% P2O5 with 81% recovery. Further beneficiation testwork was conducted in the during December 08 quarter on bulk samples collected from the costeans and included screening and scrubbing tests. Heavy scrubbing with a pebble charge produced the best results, however grades were still relatively low at around 11% P2O5 with 71% recoveries. Preliminary engineering and cost estimation studies were undertaken by the Company's Project Team looking at both a flotation circuit producing a 32% P2O5 product and simple screening circuit producing an 11% P2O5 product.
The results of these studies indicate that the drilled phosphate mineralisation is currently insufficient in overall size and thickness to be viable in its own right. Therefore, the Company is evaluating the broader region in an effort to find where the unit may become thicker and richer. To this end, the Company is in discussions with various parties who are interested in funding further exploration in the area through Farm-In arrangements.
Heron currently has some 1,900 km² of applications pending in the west Kimberley area, targeting sedimentary phosphate occurrences similar to Langey Crossing.
