Does wearing adornments made of agate (Aqiq) or jet (Sabaj) fulfill an oath to wear jewelry?

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Wearing adornments made of agate or jet does not fulfill the oath to wear jewelry. The justification is that these materials do not constitute jewelry in themselves, similar to shells (Wada') or glass beads. The argument suggesting fulfillment based on local custom (as held by Al-Shafi'i in regions where these are considered jewelry) is rejected because the counterexample of shells invalidates the principle based on local custom.