You can see here that my blue polishing cloth is slowly turning black - that is absolutely normal and is what they are designed to do.  The cloth is impregnated with a polish that helps to remove the tarnish and restore the sparkle.

You can reduce the amount of tarnish by:

• storing your silver in an airtight container when it is not being worn
• removing your jewellery before using any household cleaning products or applying body lotion
• never wearing it when getting into water - especially  swimming pools, steam rooms or jacquzzis 

But in reality we all do stuff like this and the gleam can disappear over time.  But don't panic, all it needs is a rub on an impregnated polishing cloth.  You'll be amazed at how black it turns.  Buy one here.