This sri yantra ring, the route of nine triangle  is made by the craftsman of Jaipur in India. It is made of brass (an alloy of copper and zinc).
The Sri yantra is one of the best known sacred symbols. This very old graphic representation is known for its powerful powers.

Brass is a good alternative to gold, it does not change color or decompose over time.  it does not cause allergy, so you can wear it without fear. 
It is also very easy to clean by rubbing it with a little toothpaste and lemon juice.
 
Signification:
Sri yantra: meditation, energy, concentration, creative power