labradorite

As a noun labradorite

is (mineralogy) a plagioclase feldspar mineral, calcium sodium aluminum silicate, often very coarsely crystalline, used as a decorative stone for carvings and building façades.

As an adjective undefined is

lacking a definition or value.

As nouns the difference between labradorite and obsidian

is that labradorite is a plagioclase feldspar mineral, calcium sodium aluminum silicate, often very coarsely crystalline, used as a decorative stone for carvings and building façades while obsidian is a type of black glass produced by volcanoes.

As an adjective obsidian is

black.

As nouns the difference between moonstone and labradorite

is that moonstone is (mineral) a translucent gemstone, an orthoclase feldspar, that has a pearly lustre while labradorite is (mineralogy) a plagioclase feldspar mineral, calcium sodium aluminum silicate, often very coarsely crystalline, used as a decorative stone for carvings and building façades.