Blue Kyanite Sterling Silver Ring Black Tourmaline Among the oldest documented gemstones

Among the oldest documented gemstones

the fourth stone

Mohs 5 to 6

and Roman signet rings frequently used garnet inlay

Blue Kyanite Sterling Silver Ring Black Tourmaline Among the oldest documented gemstonesA blade of blue caught in silverthe mineral's natural striations visible through the stone. Blue Kyanite is an aluminum silicate, chemical formula Al2SiO5, with a distinctive anisotropic hardness: Mohs 4. 5 along the long axis, Mohs 6. 5 across itwhich is why lapidaries work it with such care. Its color ranges from pale sky to deep sapphire, concentrated in parallel striated bands that run the length of each blade shaped crystal. This faceted stone is