The most valuable kyanite stones are dark blue in hue, with a luminous transparency and a consistent blue tint throughout the stone that demonstrates visual depth. Because of the difficulty in cutting this type of gemstone due to its cleavage features, a quality or custom cut kyanite gemstone will command a significantly higher price. Smaller beads made from lower-quality material can be used as pendants or earrings while larger cuts can be mounted on rings. Dark green, red, brown, or black colored kyanite are also valued but are less common. The color variation within a single source rock makes color differentiation difficult so these variations may have originated from different locations within the rock. Blue kyanite is the most valuable variety of the mineral because it contains more iron than other colors. Blue kyanite is rare and expensive because it requires very specific conditions for formation - extremely low levels of copper and zinc along with high concentrations of iron. These minerals inhibit the growth of crystals and cause kyanite to exhibit a transparent blue color instead. Kyanite is used by some Native Americans in jewelry because it is soft and easy to work with. They make necklaces out of bundles of kyanite fibers that they tie together with leather straps. The Navajo use orange and white kyanite to accentuate traditional designs. In conclusion, blue kyanite is the most valuable variety of the mineral because it contains more iron than other colors.