For precious stones:
* ரத்தினம் (Rathinam): This is the most common and general term for a gem or precious stone.
* மணி (Mani): This word is also used for gems, but it can also mean "jewel," "bead," or "pearl."
* விலைமதிப்பான கல் (Vilaimadippana kal): This literally means "valuable stone" and can be used when you want to emphasize the value of the gem.
For other meanings of "gem":
* முத்தம் (Muttham): This word means "pearl" and can be used for a gem that is particularly beautiful or precious.
* அழகான பொருள் (Alagāna poruḷ): This literally means "beautiful thing" and can be used to describe anything that is considered a gem, including a person or an object.
Examples:
* ரத்தினம் (Rathinam): The diamond is a valuable rathinam.
* மணி (Mani): The necklace is decorated with beautiful manis.
* விலைமதிப்பான கல் (Vilaimadippana kal): The ruby is a rare and valuable vilaimadippana kal.
* முத்தம் (Muttham): He found a beautiful muttham on the beach.
* அழகான பொருள் (Alagāna poruḷ): She is a true alagāna poruḷ.
Ultimately, the best word to use depends on the specific context.