As quite a few of other colors in the jewelry line of Pardo, the Covellite is not exactly the color of the gemstone covellite. Far from being the oil slick type of iridescence, it is nevertheless one the prettiest blues you've ever seen, and not just in a polymer clay.
It does have a very mild translucency and no pearlescence. It does beautiful mixes with other colors, especially white, platinum and translucent. Wonderful for flowers.
But the best thing it is good for - is making faux lapis lazuli. Even if the jewelry line DOES have a blue that is named Lapis, the Covellite blue is perfectly identical with the color of the real gemstone lapis lazuli of the best quality - the one that has a perfectly even blue, with no inclusions of other blue hues, or any other types of inclusions.
If you want to make a more "mixed" faux lapis, you can mix the Covellite with Lapis, or even with the Cyan or Blue of the Art Clay line.