Kyanite - (Pictured, are a matching pair of Kyanite cabochons 22.33 carat total weight).
The most desirable color is sapphire-like blue. Color is often inconsistent and unevenly distributed. Color zoning is common with most stones, which means that they exhibit multiple shades of blue in a single specimen. Streaks and blotches are common and typically white, but streaks may also form in other colors.
Stones above 2 carats can be rare and they exhibit a pearlescent luster in sunlight. Though clear stones are desirable to facet, the sapphire blue cabochons with pearlescent white steaks are desirable for use in high-end jewelry.