Argillites are highly compact sedimentary or slightly metamorphosed rocks that consist largely or wholly of particles of clay or silt but lack the fissility of shale or the cleavage characteristic of slate
Luxullianite is a rare type of granite, known for presence of clusters of radially arranged acicular tourmaline crystals which are enclosed by phenocrysts of orthoclase and quartz in a matrix of quartz, tourmaline, alkali feldspar, brown mica.