RE: ops update9 Sep 2020 18:43
with pure cassiterite containing 78.8% tin by mass we are getting a total of 68% tin in the concentrate - this puts the concentrate at a purity level of 87% pure cassiterite - this is already pretty good - see the following from the encyclopedia britannica
"Tin concentrates from the alluvial mining areas of Southeast Asia are relatively free of impurities, although there may be small quantities of related minerals such as wolframite, scheelite, and columbite. Concentrates shipped to the smelter usually contain 70 to 75 percent tin metal. On the other hand, the complex sulfide ores found in underground deposits, such as those of Bolivia, require more complicated mineral processing, often involving froth flotation, in order to produce a clean tin concentrate. Even then, Bolivian concentrates may average only 50 to 60 percent tin."
https://www.britannica.com/technology/tin-processing/Mining-and-concentrating
Pure tin is currently selling at $18100 a tonne. At 60 tonnes concentrate production per month, at a tin concentration of 68% the revenue would be USD 0.74M per month, or USD 8.9M per year. Not bad for a company currently supposedly only worth GBP 18M