pinacoidal
/pɪnəˈkɔɪdl/Crystallography
adjective
Of the nature of or relating to a pinacoid; = pinacoid; specifically designating a triclinic crystal form having a centre of symmetry; (of cleavage) occurring parallel to one of the pinacoidal surfaces of a crystal.
Origin
Late 19th century; earliest use found in Frank Rutley (1842–1904), geologist. From pinacoid + -al.