Heavy Day Sapphire

Old English hefig, weighty — cognate with heave. Used as a color modifier since at least the seventeenth century to indicate weight in saturation as much as value: heavy with pigment, heavy-bodied. In the engine's adjective grid, heavy sits alongside deep and plush in the dark-and-saturated quadrant. Closer to a fabric description than a pure value word.

Old English dæg, daylight period. As a color modifier, day implies a midday-and-broad-daylight quality, the visual register of Mediterranean-and-temperate mid-day full-sun atmospheric clarity-and-shadow open-sky working-and-walking surfaces under noon-day overhead light. Sits at the modifier-and-time end of the grid, parallel to noon and morn in usage.

An iron-and-titanium-bearing corundum — the same mineral as ruby, hardness 9 on the Mohs scale, mined for two millennia from Sri Lanka, Burma, Madagascar, and the Cashmere mines of British India. The color refers to a fine Kashmir-cut sapphire: a saturated, slightly violet-shifted deep blue with the gem's signature internal velvet — a quality of light scattering in the stone that faceted glass cannot replicate. Cooler than cobalt, deeper than azure.