Ideal joint face in radiolarian chert


I collected this in 2009 in the vicinity of the tiny village of Lykios, west of Megalopolis on Mt. Lykaion in the Peloponessos.  It is truly a special display of ideal joint properties.  Rare to find such features so well displayed.

Age & Formation
Joint fringes and plumose markings on perfect joint faces in radiolarian chert, Peloponessos, Greece. Rock is Jurassic. Jointing probably occurred in late Cretaceous and early Tertiary.