Almandine garnet

Description

This [almandine](webmineral.com/data/Almandine.shtml) garnet [Fe₃Al₂(SiO₄)₃] crystal is actually two crystals that have intergrown into the same space. This phenomenon is called interpenetrant twinning - it is a twinned crystal. Each crystal would have the form of a rhombic dodecaheadron.