All of our jewellery is made from 925 recylced Sterling Silver. It is a natural process of oxidation, that silver will tarnish. You can easily remove the black shadow with toothpaste. Take an old toothbrush, a little bit of toothpaste and simply brush it off and rinse with warm water.
The usual gold layer on jewellery is about 3µ, we use 3–5µ depending on the pieces. BISHU pieces have a thicker layer of gold than common jewellery, but nevertheless the layer will wear off after years of wearing, depending on the friction the pieces are exposed to.
If your gold pieces aren't shiny anymore you can send them to a gold-plating institute and put another thin layer on, so they will have the glow again and you can wear them for many many years. If you want us to do it for you please get in touch with us: email@example.com