Polo Resources, the AIM-listed natural resources investment group, announced that it will buy a 4.2 per cent stake in West Australian gold explorer Blackham Resources.Polo said on Wednesday afternoon it will acquire 4.76m shares at 21 cents per share for A$1m, giving it a holding of 4.2%.Blackham, listed on the Australian Securities Exchange, is focused on the development of its wholly-owned Matilda Gold Project.A sale and purchase agreement for the adjacent 1.1-1.5m tonnes per annum Wiluna plant and associated infrastructure and tenure is expected to complete this week, "re-positioning Blackham as a near-term gold producer with a substantial prospective exploration package", Polo said.The news followed an announcement earlier in the day which revealed Polo had acquired a 12.7% interest in North Africa-focused phosphate producer Celamin for A$1.2m. Sydney-listed Celamin is currently focused on the 51%-owned Chaketma Phosphate project in Tunisia and will soon be advancing a bankable feasibility study.The stock was down 5.2% at 16p by 15:29 on Wednesday.BC