I had a purebred Silky, we lost her 4 yrs ago at 14 1/2 yrs old. Her coat would grow right to the floor and was a perfect steel blue with tan head and markings exactly the same as a yorkie. However she weighed about 9 1/2 lbs. which is right for the standard. We got her instead of a yorkie at the time because we had small children at home and silkies are definitely sturdier than yorkies. She was an absolutely lovely dog, we still miss her very much.
If you have a bit bigger than normal yorkie and a bit smaller than normal silky most people would not be able to tell them apart.