South Crofty and United Downs Mine Locations
With the acquisition of the South Crofty tin project in July 2016, Strongbow also acquired additional mineral rights in Cornwall, UK. The additional mineral rights cover an area of approximately 15,000 hectares and are scattered throughout Cornwall and include the United Downs Project. United Downs is located approximately 8km east of South Crofty and lies within a densely mined district, historically referred to as Gwennap. Gwennap was the richest copper producing region in Cornwall (and the world) in the 18
th and early 19 th centuries, and at that time was referred to as “the richest square mile on earth”;
In January 2017 Strongbow entered into an agreement with Cornish Lithium, whereby Cornish Lithium has the right to explore Strongbow’s mineral rights in Cornwall for lithium in brine occurrences while Strongbow retains the rights to any hard rock mineralisation.
United Downs Project - an Overview
The United Downs project covers, or is located immediately adjacent to, four former copper and tin producing mines: Consolidated Mines and United Mines to the west; and, Mount Wellington and Wheal Jane Mines to the east. The main mineralised structures in all four mines trend ENE and dip steeply to the north. All of the mineralisation exploited historically is related to either quartz veins or quartz-tourmaline veins hosted within “killas”, the local name for metasedimentary rocks that overlie granite intrusions.
At the nearby South Crofty Mine, copper-tin-zinc-tungsten mineralisation hosted within the killas passes into tin mineralisation at depth as the mineralised vein-like structures pass into the underlying granitic host rock. The same zonation potentially exists at United Downs, where only the killas-hosted mineralisation has been exploited to date. The underlying granite, which is a target for further tin mineralisation, was encountered in GWDD-002 between 300 and 600m and again at 700m vertical depth.
The nearby Wheal Jane mine was discovered and developed into a modern mine in the late 1960s, initially by Consolidated Goldfields, and thereafter by Rio Tinto Zinc. Mining activities at Wheal Jane ceased in early 1991, due largely to the Tin Crisis of 1985, but processing of South Crofty ore continued until March 1998 when ongoing low tin prices forced its eventual closure.
As part of the intense exploration period that Cornwall enjoyed between the 1960s and 1985, an underground exploration drive was developed during the 1980s westwards from Wheal Jane through Mount Wellington mine at 6 level elevation, whilst an exploration decline (the Wheal Maid decline) was developed to explore for tin mineralisation similar in style to that which was exploited in Mount Wellington and Wheal Jane mines. This exploration work was stopped after the tin price collapse in 1985, despite the great promise for the discovery of polymetallic mineralisation
A New Copper Tin Discovery
In April 2020, Strongbow reported the discovery of a new zone of high grade copper-tin mineralisation located in a previously unmined area between the historic United Mine and Consolidated Mines at United Downs. The discovery was made in drill hole GWDD-002, drilled by Cornish Lithium. Two diamond drill holes have been completed, for a total length of 1,858m and at the time of writing, only results from part of diamond drill hole GWDD-002 have been reported so far.
Diamond drill hole GWDD-002 was drilled by Cornish Lithium to test the potential for lithium in brine at United Downs, within the historic Gwennap copper and tin mining district;
GWDD-002 intersected semi-massive sulphide mineralisation between 90.60m and 105.29m downhole depth;
Assays returned 14.69m grading 7.46% Cu, 1.19% Sn, and 0.15% Zn from 90.60m to 105.29m downhole length;
Further drilling is required to confirm true width, as well as the strike and dip of the mineralised zone;
Three individual sample intervals returned assays greater than 20% Cu – final results for these overlimit assays are pending, and will be reported when received;
The semi-massive sulphide mineralisation is similar in style to that mined at Wheal Jane and Mount Wellington mines, located 1.5km along strike to the east; and
Copper grades reflect recorded historical mine production from United Mines located approximately 200m to the south.
Mineralisation looks like it runs very close to the decline at the old Wheal Maid mine which could make accessing the mineralised lode underground quicker and simpler depending on the conditions of the decline today.
Processing of ore from the newly discovered lode could be done at South Crofty which is fully permitted for mineral processing and is about 8kms west from the United Downs site.
Plans Going Forward
Strongbow is in the process of logging and sampling the remaining drill core from both GWDD-001 and GWDD-002, and is applying for a drill permit to drill test the strike extension of the lode structure intersected in GWDD-002.
United Downs Mineral Rights held by Strongbow