Moonmilk

Creamy, cave-crystallized carbonates

Moonmilk is a white, creamy substance found inside limestone, dolomite, and possibly other types of caves. It is a precipitate from limestone comprising aggregates of fine crystals of varying composition, usually made of carbonates such as calcite, aragonite, hydromagnesite, and/or monohydrocalcite.

This keyword could refer to multiple things. Here are some suggestions: