What precious stone's name was derived from the Greek word meaning "unconquerable"?

More Questions:

The Tour de France was first staged in which decade?

In which decade were the first Winter Olympic Games held?

Which series of novels refers to its main character as "The Last Gunslinger"?

Who created James Bond?

According to legend, Robin Hood was born in what area of Nottinghamshire?

What two rivers does the Nile split into?

What countries share a land border with Somalia?

What planet was the first to be discovered by mathematical prediction and not observation?

Triton is a moon of which planet?

How many carbon atoms are there in an aspirin molecule?

Beavis and Butthead worked part-time where?

What 1984 #1 song by the duo Wham! charted again in 2009 when covered by the group Seether?

Who was the lead singer of the band Motorhead?

Who won a Grammy Award for his song "Mack the Knife"?

Whose concert was the target of a terrorist attack in May, 2017, in Manchester, UK?