botryoidal
/ˌbɑtriˈɔɪdəl/
adjective
- Having a form resembling a bunch of grapes; composed of rounded, clustered masses.
- Botryoidal formations are common in certain types of agate and chalcedony.
- The cave walls were covered in botryoidal calcite deposits.
- The botryoidal hematite looked like a cluster of shiny black grapes.