ir‧re‧place‧a‧ble /ˌɪrɪˈpleɪsəbəl◂/ adjective
too special, valuable, or unusual to be replaced by anything else:
Works of art were lost, many of them irreplaceable.

[TahlilGaran] Dictionary of Contemporary English ▲

valuable worth a lot of money and expensive to buy:
a valuable piece of jewellery
The carpet is extremely valuable.
priceless so valuable that it is impossible to calculate a price:
a priceless painting by Rembrandt
The statue is priceless.
precious metal/stone precious metals such as gold, or stones such as diamonds are very rare and expensive :
Back in ancient times, coins contained precious metals.
The ring was set with dozens of precious stones.
worth a lot/a fortune informal to be worth a very large amount of money:
Some rare baseball cards are worth a fortune.
precious very special and important to someone - used about people or things:
My family have always been precious to me.
His free time was very precious to him.
the place where I kept my most precious things
prized very special and important to someone, so that they want very much to keep them or obtain them:
The book was one of his most prized possessions.
The shells are prized for their beauty (=are considered to be very special).
treasured very special and important to someone, especially because it is connected with someone they love:
the case in which she kept her most treasured possessions
The holiday was now a treasured memory.
a treasured gift from her grandmother
irreplaceable extremely special and important, especially because it is the only one of its kind:
The manuscripts are said to be irreplaceable.

[TahlilGaran] English Thesaurus ▲