I have a silky terrier- they are very similar to a yorkie, but usually larger, longer in body than a yorkie. Bailey is about 14lbs- he is longer than he is tall. Not all silkies are that big- my vet told me she has seen silkies smaller than my yorkies and yorkies bigger than my Bailey. But in general I think they tend to be larger than 6-7lbs. I attached a picture of him alone sittin' pretty and another picture of him with Macie so you can get an idea of his size and shape compared to her (in this picture Macie was about 4.5lbs)
He has the same hair color and texture as a yorkie, but his hair doesn't seem to grow as fast. Also his hair is really wavy on his back-half. I'm not sure if this a silky terrier thing or what. I have a friend who also has a silky and his hair is wavy on his butt too! We think it's funny
Here is a link to the AKC standards for Silky Terriers:
http://www.akc.org/breeds/silky_terrier/index.cfm