Substances the Calm the Spirit

What special cooking instruction should be followed when preparing Mu Li (ostrea concha) in decoction?

It is more difficult to extract the medicinal qualities from shells and minerals. Therefore they require a longer cooking time.

Source: Bensky, D. (2004). Chinese Herbal Medicine: Materia Medica. Seattle, WA: Eastland Press. pp. 913 [Q1176]