Lapis is a rock and not a mineral because it is made up from various other minerals. To be a mineral it would have one constituent only, and Lapis has several including Lazurite, Sodium, Aluminum, Silicon, Oxygen, Sulfur and Chlorine. Most Lapis contains Calcite, Sodalite and Pyrite. The best color is an intense blue that is lightly dusted with small flecks of Pyrite. Lapis takes an excellent polish and has been made into jewelry, carvings, boxes, mosaics and ornamental objects.
Iolite is the gem variety of Cordierite. Iolite can be light to deep blue and usually has a purplish tinge to it. The name “iolite” comes from the Greek word for violet. Another old name is dichroite, a Greek word meaning “two-colored rock”, a reference to cordierite’s strong pleochroism. It has also been called “water-sapphire” and “Vikings’ Compass” because of its usefulness in determining the direction of the sun on overcast days, the Vikings having used it for this purpose.