Cornish Metals Inc., the owners of South Crofty Mine have reported further good results from its diamond drilling programme.
A new hole called ‘SDD20-001’ was drilled to test multiple tin-bearing vein-like structures (“lodes”) in the central section of South Crofty Mine, going below any historic mining on this lode.
Three lodes have now been intersected and results came back with an average of 2.19% tin.
For context, the geologically similar Renison Bell underground tin mine in Tasmania mined an average grade of 1.32% tin in 2019.
Additional lode structures with visible tin mineralisation have been intersected deeper in hole SDD20-001, the results for which will be released as assays are received and tabulated.
Richard Williams, CEO of Cornish Metals said “The Intermediate Lode structure was predicted by our geological team to be in this area but such a high-grade intersection so far beneath the old mine workings was not anticipated, it does reinforce the exploration potential at South Crofty and our ability to find economic structures within areas of the mine that have been previously overlooked.”
The diamond drilling programme commenced in June 2020. The programme is designed to test drill targets beneath mineralised lodes that were being mined up until the closure of South Crofty mine in 1998. Additionally, the programme is designed to test the suitability of directional drilling combined with “wedges” to produce multiple intersections of vein structures from a single surface or underground drill hole as a means to undertake resource definition drilling and a path to completion of a feasibility study. This initial programme comprises up to 2,000 metres of diamond core drilling from a single surface parent hole and up to three daughter holes that will be wedged-off the parent hole. In addition to the parent hole, the first daughter hole has been completed, and a second daughter hole is currently being drilled.
The historic South Crofty mine was a high-grade copper producer from the late 16th century up until the mid-19th century, when it transitioned to being a high-grade tin producer, with more than 100,000 tonnes of tin metal produced between 1906 and 1998. The current project benefits from an active 50 year mine permit, planning permission to build new surface processing facilities, environmental permits to dewater the mine, and very strong local and national support to see the mine reopened.
In simple terms, the geology at South Crofty can be divided into two main rock types; metasediments (called “killas” in Cornwall), which overlie an intrusive granite body. The vast majority of copper has been mined from the killas, while nearly all tin produced at South Crofty has been mined from the underlying granite.
SDD20-001, drilled at an angle of -60o to the north, passed from killas into the underlying granite at a downhole depth of 260m. The drillhole intersected a mineralised structure between 620.6m and 623.26m down hole depth, which correlates with Intermediate Lode, previously mined at shallower depths to the 245 fathom level (440m below shaft collar). The geology consists of a quartz mica mass with strong haematite alteration, with a strong stockwork of dark tourmaline veining intensifying to a breccia at the base of the interval. Fine patches of cassiterite occur within the quartz zones of the structure.
The annual global demand for tin is approximately 370,000 tonnes of refined metal with the primary use being for solder in high-tech industries such as consumer and industrial electronics, computing, IT networks, power generation and power supply, essential for the transition to a low-carbon economy.
It is also a vital component of Indium-Tin Oxide touch screen technologies, solar PV cells, and increasingly as advanced anodes in various types of lithium ion batteries. More traditional industrial uses include the stabilising of PVC plastics, glass floating, tin plating of steel and the manufacture of important industrial alloys including bronze and white metals.
Cornish Metals (formerly Strongbow Exploration Inc) completed the acquisition of South Crofty plus additional mineral rights located in Cornwall in July 2016. The additional mineral rights cover an area of approximately 15,000 hectares and are distributed throughout Cornwall. Some of these mineral rights cover old mines that were historically worked for copper, tin, zinc, and tungsten.
South Crofty mine closed in 1998 following over 400 years of continuous production. Cornish Metals has successfully applied for and received the necessary environmental permits to abstract, treat and discharge mine water in order to dewater the mine. Planning permissions for the operation of the mine and re-development of the surface facilities have been secured and construction of the water treatment plant foundations commenced. The dewatering pumps, variable speed drives and new high-voltage power supply have been delivered to site.