Significance of the green stone?

[Lostgaeriel]

'It needs more to make a king than a piece of elvish glass, or a rabble such as this...'

Now that Voralphion has drawn attention to this quote, I find it a little confusing.

I don't know if Sauron's mouthpiece was referring to the Elendilmir or to the Elessar (or to something else?). How does one interpret 'elvish glass'? Elessar = Elf-stone = green beryl = emerald but the Elendilmir was a white jewel = diamond?

I assume Aragorn was wearing the Elessar eagle brooch when he looked into the palantir and at the Black Gates. When Galadriel gave it to him, he pinned it upon his breast. And I doubt he took it off any time after that; it was a token of hope.

The Elendilmir would be the object to 'make a king' since it was the 'crown' of the North Kingdom, Arnor. But at the Black Gates, Aragorn would not yet be in possession of either the Elendilmir or the tall winged crown, so how could the Mouth of Sauron be referring to the Elendilmir?