Joints are brittle fractures where the walls have not undergone significant displacement parallel to the fracture plane. There may be significant displacement perpendicular to the fracture, however, and when the resulting space is filled by minerals then the fracture is called a vein.
Joints in limestone, weathered to produce karstic 'clints' and 'grikes'. Early Ordovician St. George Group, Port au Port Peninsula, southwest Newfoundland (© G.S. Stockmal 1998)
En-echelon tension gashes. Mesozoic-Cenozoic Amaliapolis Complex, Othrys, Greece
Fibre-filled vein. Bray Group, Southeast Ireland