Antimony's ore, stibnite, is identified as antimony trisulfide, Sb2S3, and the smelted metal is identified as elemental antimony, Sb, a metalloid element with chemical behavior intermediate between a true metal and a non-metal, both identifications well supported and essentially uncontested. What remains genuinely unsettled is antimony's place in the classical planetary scheme: unlike the seven metals proper, gold, silver, mercury, copper, iron, tin and lead, each tied by long convention to one of the seven planets, antimony was sometimes treated by alchemical writers as a kind of eighth, ambiguous metal, associated inconsistently with different planets or, in some interpretive traditions, treated as belonging to no single planet at all, a genuine disagreement in the historical sources rather than a gap in modern scholarship. This entry deliberately leaves the planetary attribution unassigned rather than picking one contested claim over another, consistent with how the sources themselves disagree. Basil Valentine's own text repeatedly stresses antimony's dual, contradictory nature, at once a valuable medicine and a genuine poison, a characterization that any single fixed planetary attribution would tend to flatten rather than honor.