Baddeleyite is a rare, naturally-occurring form of zirconium dioxide, or zirconia, which can occasionally be encountered as a collector’s mineral but is almost never faceted. While some baddeleyite crystals are light yellowish and/or brownish, or even colorless, the mineral tends to be most commonly associated with a very dark brownish coloration that verges on black. These stones may also possess a distinctive submetallic luster, and are generally opaque when not cut into thin slices.

First discovered in Sri Lanka by a railroad superintendent called Joseph Baddeley, baddeleyite’s composition is actually identical to that of the well-known synthetic diamond simulant cubic zirconia (CZ). However, the contrasting crystal forms possessed by these two polymorphs give rise to some vastly differing visual and physical attributes, including baddeleyite’s significantly lower hardness (6.5).