Blue Labradorite; the above 8x6mm oval cabochon is set in a nicely handmade Silver ring.
Labradorite is a form of “Feldspar”, the same crystalline family of Moonstone. It was not identified separately as a gemstone until the late 1770s when deposits were discovered in Labrador (hence, of course, its name). Its interior structure creates with light an iridescence, a vivid sheen, called “labradorescence”, which shows itself very distinctly blue the paler the gemstone.

Labradorite, like Moonstone, is not a tough gemstone; Quartz is considered tough; any gemstone more tough than Quartz is really tough, anything less tough than Quartz is considered less durable, and Labradorite is that. However, its relative softness has not dented its popularity, indeed it is a quite popular semi-precious gemstone, especially when it is Moontone-ish in colour and it has the distinct sheen of the above Blue Labradorite.
The main problem with Labradorite, as with Moonstone, is that with careless wear the surface of the gemstone can get scuffed. The more the surface is scuffed, the less bright and luminous its sheen. It is a gemstone requiring care.