(1) The crystals are typically tetragonal dipyramids with pinacoids.(2) Small, black, tetragonal anatase crystals associated with rutile were found on microcline by Kile.(3) The crystals are stepped tetragonal pyramids (somewhat resembling anatase) associated with chrysocolla.(4) Xenotime crystals exhibit tetragonal prisms, dipyramids, and pinacoids, whereas zircon may exhibit first- and second-order tetragonal prisms, dipyramids, and pinacoids.(5) Rutile is a tetragonal mineral famous for its variety of crystal habits and twinning.(6) Zircon (variety cyrtolite) commonly forms curved tetragonal crystals that radiate from a base of biotite crystals and terminate in adjacent feldspar.(7) Superb, equant tetragonal crystals occur on quartz in the junction pockets.(8) Furthermore, we see that the molecular rows along the a axes are in perfect alignment with the underlying layers, as one would expect for the tetragonal lattice of the CO-HbC crystals.(9) Narsarsukite is another tetragonal mineral that can show a tetragonal prismatic habit, particularly when it develops in open cavities.(10) In addition, Tetragonocrinus has tetragonally positioned accessory canals along the column.(11) The secondary thermal aging process requiring tight manufacturing controls for proper microstructural development has limited the supplier base for the tetragonally toughened zirconias.
