If you are searching for the darkest, richest color within topaz gemstone, then you should try London blue topaz – the treated variety of topaz famous for its inky blue color. The specialty of this treated topaz variety is that they do not cost much, and perhaps this is why it is used in making beautiful London blue topaz rings and other jewelry items. If you are thinking of adding this gemstone ring to your jewelry collection, you need to make the correct choice of metal that suits your personal preference, and you also need to know which jewelry pairs well with the ring. There are several options that are available when it comes to metal selection for a London blue topaz ring. If you are on a budget, then you should definitely opt for 925 sterling silver.