Matches: Dwarves have never taken to these.
Isildur's Bane: It betrays in the roundest manner.
Silmarils: Narnian prince begins to reside in hobbit dwellings? Such a mingling! See them shine!
Chalcedony: Heavenly start to December contrives to shield a mariner’s sword.
Emerald: Leader in disarray gains a thousand: a jewel to adorn a steersman.
Laughter of Mordor: Lalaith in the dark land? Serves quarrellers right, some might say!
Lamps of the Valar: Objects of heavenly beings impersonating Miss Nightingale?
Arkenstone: Sounds like Noah’s vessel cast in granite! Resplendent thing.
Night of Naught: Day’s opposite becomes null, in song.
Years of the Trees: Happy days, and light ones.
Correct answer and reasoning. Well done! And over to you.
(Quite what use a quartz scabbard would be to the average soldier I don't know, but it's Earendil's ... all his accessories are shiny and precious and more mythical than practical. And maybe Bilbo imagines half of the precious/semi-precious substances for the poem). (And I really wanted an excuse to have the word chalcedony in a password).
Apologies for the delay. I was writing this reply when the battery ran out, and then was called away on errands.