Rather than exploiting native copper or copper ores as in Southwest Asia, the earliest copper objects in Central, Northern and Western Europe were smelted from oxidic and sulphidic ores and appear concurrently with other forms of metal exploitation, including silver cupellation
in Sardinia by the early fourth millennium BC (Lo Schiavo et al.
Martyn felt the piece should include appropriate symbolism so his design depicts the structure of the Palladium atom, vibrantly coloured flames to represent the traditional cupellation
method of fire assaying and a typical "read out" from an X Ray fluorescence machine which uses the latest technology to assay pieces prior to hallmarking.
Consider Leibniz's definition of gold: "gold is a metal which resists cupellation
and is insoluble in aqua fortis; that is a distinct idea, for it gives the criteria or definition of gold.
We have observed that the unique poly-metallic nature of the El Capitan deposit results in significant slag and/or cupellation
losses when using lead collection fire assay, and the oxide nature of the deposit does not lend itself well to the application of nickel sulfide fire assays techniques typically used in sulfide PGM deposits.
In north-east Wales (Clwyd), by contrast, the majority of mines (including all of those surveyed for the project) lie within the Flintshire/Denbighshire orefield, where veins of lead and zinc ores (not 'silver ores', at least at macroscopic level--the silver is an impurity in the lead ore, recovered by cupellation
from the smelted lead) are hosted by gently-dipping carboniferous limestone, forming upland pasture with a reasonable amount of settlement.