The mechanic

A mineral's streak is the colour of its powder, and it routinely contradicts the lump. So the archive is ordered by measured streak hue angle rather than by date, and the ground sits in the empty 111.8° arc the fifteen streaks leave behind.

The control case. Quartz is harder than the plate, so it cuts the porcelain instead of powdering on it — 0.42% coverage against a 2% floor. No colour, no hue angle, no position: its field is painted in the ground and it sits outside the order.