Onycha

Three of the four ingredients Exodus 30 names for the incense of the sanctuary are reasonably secure. The fourth, shecheleth, is not. The Septuagint renders it onycha, which means fingernail or claw, and every identification since has been an argument about what that word was translating.

The leading candidate is the operculum, the horny plate with which certain marine gastropods seal their shells. It does look like a fingernail, it was traded as an aromatic in the ancient Near East under names that fit, and treated with an alkali and burned it gives a musky animal smell that works in a compound. Arab and later European sources describe exactly this material under the name blatta byzantina.

The difficulty is halakhic. A sea snail is not kosher, and an ingredient of the temple incense being a non-kosher animal product needs explaining. Several authorities accept it on the ground that the incense is not eaten; others reject the identification for that reason and look elsewhere.

The alternatives are all plants: benzoin, labdanum, a rockrose resin, or the bud of a clove-like tree. None of them accounts for the fingernail sense of the Greek.

The stakes are practical. Any attempt to reconstruct the ketoret has to decide, and there is no evidence that would settle it short of a residue analysis from a temple-period vessel.

The onycha problem is a useful specimen of how much of ancient religious material culture is unrecoverable, and how quickly. The temple stood; the incense was compounded daily by a named family; the ingredients were written down in scripture and elaborated in the Talmud. And within a few centuries of the destruction, the second name on a four-item list could no longer be matched to a substance.

Part of the reason is that ancient aromatic names are trade names rather than botanical ones. They travel with the goods, they shift as the source shifts, and a name that meant one resin in the eighth century BCE can mean a substitute by the second century CE without anyone recording the change. Frankincense, myrrh, cassia, cinnamon and nard all have this problem to some degree; onycha simply has it worst.

The other part is that smell leaves no archaeology. A vessel survives, a pigment survives, a text survives. The compound that was burned in it is gone unless a residue happens to be trapped and someone thinks to analyse it, and gas chromatography of temple-period incense residues is a very small literature.

The atlas records the identification as open rather than picking one, and there is an open question filed against it. A confident answer here would be a guess dressed as a fact.