Tetragonal, well-terminated, lustrous, blackish-green crystals of wiluite Ca19(Al,Mg)13(B,◻,Al)5(SiO4)10(Si2O7)4(O,OH)10 aesthetically perched on top of its matrix; Vilyui River Basin, Sakha Republic, Eastern-Siberian Region, Russia; biggest crystal 3 x 2 x 2 mm