I think an Orb is more of a function than a form. For the purposes of ponderance – classically the primary function of the Orb – an Orb can serve its purpose regardless of the rotundity of its profile or the luminosity of its core.
In this sense, to ponder the humble coffee cup, the raindrop, or the Depths, would turn these concepts, for the time being, into one's Orb.
Of course, the familiarity, the Platonic ideal of the orbular Orb, gives such an object perhaps more power (in the pondering sense) than, say, a less reified Orb (such as the Depths).
Additionally, the orb-as-repository function of the classic crystal/glass/stone Orb entails significant advantages over the more ephemeral raindrop-Orb.