Cornish Metals (previously Strongbow Exploration) began the drilling programme in June 2020, which was designed to test targets beneath previously-mined areas. These mineralised vein-like structures, or “lodes”, were mined up until the mine closed in 1998.
Early results, published in September, were positive. Initial intersections with two lodes returned mineralisation averaging 2.22% Sn. In the context of tin deposits, this is considered high-grade, with the global average tin resource grade around 0.8% Sn. However, the grades assayed are “in line with the historic production grades from the South Crofty Mine and our Mineral Resource Estimate”, according to Cornish Metals CEO Richard Williams.
The most recent drilling results are even more positive. High-grade mineralisation was found below the historic mine working, including 2.6m of drill core with an average tin grade of 10.33%. This includes a 0.46m section with an average grade of 39.6% Sn. “Such a high-grade intersection so far beneath the old mine workings was not anticipated”, according to Richard Williams, although “the Intermediate Lode structure was predicted by our geological team to be in this area.”
Overall, Williams believes the drilling programme has been a success. “The 2020 drill programme at South Crofty has successfully achieved its two primary objectives”, he said, “the results confirm high-grade nature and persistence of known mineralised structures within South Crofty“. As well as producing strong geological results, the drilling programme was also designed to test the suitability of different drilling techniques. Due to the success of the drilling programme, these methods can be used to undertake further resource definition drilling and represent “a path to completion of a feasibility study”.
However, there was also “a third, pleasant surprise of the programme”, according to Williams. Five new, mineralised lodes were found between, and adjacent to, historically mined lodes within the South Crofty mine. Cornish Metals also recently reported the discovery of high-grade mineralisation at the nearby United Downs project. The combination of the two “demonstrates the exploration potential at both South Crofty and Cornish Metals’ extensive tenure holdings across Cornwall”.