Plocoid

Plocoid is a term used in crystallography to describe a specific type of crystal habit. A plocoid crystal is characterized by being roughly spherical and often develops an uneven or bumpy surface. These crystals are typically composed of many small, interlocking crystalline units that collectively form the overall rounded shape. They are not truly smooth spheres but rather appear as aggregates of smaller crystalline elements. Plocoid forms can occur in various minerals and are often a result of specific growth conditions during crystallization. The term is derived from the Greek word "plokos," meaning lock of hair or tuft, which alludes to the somewhat tangled or clustered appearance of the constituent crystals. While not a formal classification of crystal structure, plocoid describes a common and recognizable external morphology.