koh-i-noor
noun
ˈkōəˌnu̇(ə)r
plural koh-i-noors
often capitalized
: something that is or is felt to be the best of its kind
especially : a usually large and valuable diamond
a young Spaniard with a Koh-i-noor of a diamond on his finger and pearls the size of camphor balls in his shirt front 
W. J. Locke
W. J. Locke 
Word History
Etymology
from Koh-i-noor, famous diamond that became part of the British crown jewels after the annexation of Punjab by Great Britain in 1849, from Persian Kōh-i-nūr, literally, mountain of light