The Collaborative International Dictionary
Zirconoid
Zirconoid \Zir"con*oid\, n. [Zircon + oid.] (Crystallog.) A double eight-sided pyramid, a form common with tetragonal crystals; -- so called because this form often occurs in crystals of zircon.
Wiktionary
zirconoid
n. (context crystallography English) A double eight-sided pyramid, a form common with tetragonal crystals; — so called because this form often occurs in crystals of zircon.