Mother-of-Pearl (Nacre Shell) zhēn zhū mǔ · 珍珠母

Concha Margaritifera (nacreous shell of Hyriopsis cumingii, Cristaria plicata or Pteria martensii)

Nature and flavour. Salty and cold; Liver and Heart systems.

Classed as calming the Liver and anchoring yang, as calming the spirit and settling fright, and as clearing the Liver and brightening the eyes. It is the shell the pearl grows in, and it is used in the classical framework for the same rising-yang presentations as 石决明 — headache, dizziness, tinnitus — with the difference that the traditional sources also give it the spirit-calming and fright-settling action, which is not recorded for 石决明. The pearl itself, 珍珠, is a separate entry in the materia medica.