Marble inlay is a form of ornamentation that involves fitting and securing pieces of marble into corresponding spaces cut into another stone surface to create a design while maintaining the base surface's original form.1 Marble inlay is absorbed as part of the building's form; this is the opposite of applied ornamentation, an example being the blind arches that are applied to Humayun's Tomb's facades. Applied ornamentation itself, for example, the dado on the facades can and does have marble inlay as part of its own surface. In the context of Humayun's Tomb, marble inlay does not include the design element that appears in later Mughal architecture, pietra dura.
The most striking example of marble inlay at Humayun's Tomb is the stellate marble inlay cartouche that divides the surface of the dark red sandstone plinth and creates a uniform space for each arched opening.
Humayun's Tomb's structural elements are dynamically articulated with marble inlay that is contained vertically by the white marble engaged colonettes that run the height of each corner of the tomb's facades. On Humayun's Tomb's facades, a white marble inlay arch outline joins two sandstone door jamb engaged colonettes to encase each facade opening that originates from the plinth terrace. The same is true for all of the arched openings on the plinth.
1. R. Nath, (Ajmer: The Heritage, 2018) chap. 1, Kindle.
2. ibid, chap. 1.