Black Labradorite

Labradorite occurs in mafic igneous rocks such as basalt, gabbro and norite and in anorthosite. According to Geology.com, a significant amount of gray to black labradorite with good labradorescence is produced in Madagascar and Russia, while the best-colored Finnish material is sold as spectrolite.

The name describes only the dark body color; the material is ordinary labradorite and has the same hardness, density and cleavage. Its labradorescence comes from light reflected inside the stone and appears only at certain viewing angles; not every labradorite shows it. Pascle notes that dark material is also sold as "blue labradorite", a name that refers to a blue flash rather than to the body color. Larvikite, a Norwegian rock rich in ternary feldspar, also shows a blue sheen on a dark ground but is a rock, not labradorite, so a dark stone with blue flash should not be assumed to be labradorite from its look alone.

Labradorite has a Mohs hardness of 6 to 6.5 and two directions of perfect cleavage, so it can break from a sharp knock and scratches more easily than harder gems such as sapphire or agate; Geology.com advises caution in jewelry exposed to impact.