Useful Zenith Turquoise

Latin ūsus, use — adjectival suffix -ful. As a color modifier, useful implies a clear-and-purpose-serving quality where the hue carries the visual register of helpful-and-supporting design-element. Sits at the crisp-and-functional end of the grid, parallel to practical and serviceable in usage.

Arabic samt-al-ra's, path-overhead. As a color modifier, zenith implies an overhead-pointing-and-high-point quality, the visual register of celestial-sphere-and-overhead-Zenith hand-overhead-pointing-and-high-point celestial-sphere-and-overhead-and-Zenith-pole zenith-and-overhead-pointing-and-high-point surfaces under celestial-sphere-and-overhead-and-Zenith-pole astronomical-and-celestial-mechanics overhead-axis-light. Sits at the modifier-and-cosmic end of the grid, parallel to nadir and axis in usage.

The hydrated copper-aluminum phosphate mined in Persia and the American Southwest for thousands of years — the firuze of Iran, the chalchihuitl of Mesoamerica, the heart of Pueblo and Navajo silverwork. The color refers to a fine Sleeping Beauty turquoise from Arizona: a saturated, slightly green-shifted blue with the slight matrix of host-rock veining. Brighter than persian, lighter than cerulean.