gem
n. countable B1 Intermediate US //ˈdʒɛm// UK //dʒˈɛm// gem
n. a precious stone like a diamond or ruby that is cut and polished for jewelry. It can also describe a person or thing that is especially helpful or excellent.
n. a precious or semi-precious stone, especially one cut and polished for use in ornamentation. Figuratively used to denote a person or object of exceptional quality or value.
The ring features a bright green gem.
The small museum is a hidden gem that most tourists miss when visiting the city.
Geologists identified the specimen as a rare gem, noting its flawless clarity and unique refractive properties that distinguished it from common quartz.
Usage
Often used metaphorically with the adjective 'hidden' to describe an excellent but little-known place.