what can be used as a noun to describe something valuable?

I am trying to write a little story, and I need a word to fit in this sentence
"The necklace that appeared on her neck was a _______"
I need a one word noun that means "something valuable, expensive"
any suggestions?

Treasure.

SoothingDave said:

Treasure.

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I thought of treasure, and I thought of trophy, but these are very big words to describe just one valuable object!

Luxuriant?

luxuriant - definition of luxuriant by the Free Online Dictionary, Thesaurus and Encyclopedia. (#3)

A luxuriant?

That sounds good, can it be used as a noun as well as an adjective?

Maria311 said:

That sounds good, can it be used as a noun as well as an adjective?

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No, it can't. That's why Mike put a question mark after it.

Rover_KE said:

No, it can't. That's why Mike put a question mark after it.

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But he put an "a" before it.

Maria311 said:

But he put an "a" before it.

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Yes, he was asking charliedeut if he was really suggesting that "a luxuriant" was correct?

Yes, I did. I put the article before it so the question mark would indicate that it was not a noun. I understand that my post was confusing.

And charliedeut himself can confirm that it was a silly mistake to give an adjective when a noun was in need .