Tin

Tin was smelted chiefly from cassiterite, tin oxide ore, found concentrated in a comparatively small number of major deposits across the ancient world, notably in Cornwall in Britain, in the Iberian peninsula, and in central Asia, a geographic concentration that made tin one of the most actively traded metals of the Bronze Age, since bronze, an alloy of roughly nine parts copper to one part tin, required a reliable tin supply that few regions could produce locally even where copper itself was abundant. Tin melts at a notably low temperature compared to the other classical metals, is soft enough to be worked without great difficulty, and takes a bright, silvery finish, properties that also made it useful on its own for vessels, ornamental work, and, alloyed with lead, for pewter tableware widely used across medieval and early modern Europe.

A genuinely striking property of tin, observed though not explained until modern solid-state chemistry, is what is now called tin pest: prolonged exposure to sustained cold causes ordinary metallic tin to slowly convert into a crumbling, grey, non-metallic allotrope, a transformation that can spread through contact like a contagion across a stored tin object, destroying its structural integrity, a phenomenon historically blamed, memorably though anachronistically, for button failures on Napoleon's army uniforms during the bitterly cold Russian campaign, a colorful story historians treat with appropriate caution given the difficulty of verifying it against the documented timeline and conditions.

Tin's pairing with Jupiter is consistently attested across the alchemical tradition, and its symbol, a crescent set above a cross, is identical to the astrological glyph for Jupiter, though the underlying reasoning behind this particular metal-planet pairing is less immediately intuitive than iron's link to Mars or gold's to the Sun, and historians of alchemy generally treat the seven metal, seven planet correspondence as a systematic, largely a priori scheme, seven metals matched to seven known planets in a fixed traditional order, rather than one where every individual pairing needs its own separately motivated justification.

Tin's comparative softness, its position in the middle of the traditional hierarchy of metallic perfection between the base heaviness of lead and the refined stability of gold, was read by some alchemical writers as reflecting Jupiter's own traditionally benevolent, moderate astrological character, a symbolic reading applied after the fact to a pairing whose original basis may simply have been the need to complete a matched set of seven. Tin's own tin pest transformation, though unrelated to its planetary symbolism, offers a fitting closing irony: a metal associated with Jupiter's supposed benevolent stability turns out, under the right cold conditions, to be one of the least structurally stable of the seven classical metals.