Brass:
Some jewellery I make is made with Brass. I use this to provide gold-coloured jewellery that is less expensive than gold.
Brass is as yellow alloy of zinc. Resembling a gold colour. I wax all my brass pieces. However all metals will naturally tarnish, giving your piece an aged look.
The copper in the brass can cause greening on the skin, this is a common reaction between your skin and the metal. It will wash off or fade.
To bring back shine you can always use a polishing cloth for jewellery.
Gold-filled:
For certain elements I can use Gold-filled. Gold-filled is composed of a solid layer of gold mechanically bonded to a base of either sterling silver or some base metal. The metal is easy to care for and will usually maintain its golden shine for a lifetime.
I always mention which elements are made in Gold-filled or Brass.