Besides them being two different breeds here are the breed specs..from the Dogs In Canada website:
Silky Terrier:
Origin: Primarily a blend of the Australian and Yorkshire Terriers, the Silky was developed in Australia in the early 1900s. Differing opinions led to two separate standards being drawn up Ð one in Sydney and the other in Victoria. In the first instance, the breed was known as the Sydney Silky Terrier and in the latter it was called the Victorian Silky. In 1959, the Australian National Kennel Council adopted a single standard and renamed the breed as the Australian Silky Terrier. The breedÕs sole purpose has been to serve as an attractive and delightful household pet.
Temperament: Quick, friendly, inquisitive and responsive, the Silky retains the keenly alert air of the terrier. His joy of life makes him an ideal companion for any size accommodation.
Activity Level: Neither as active as a terrier nor needing as much care as the more diminutive Toy breeds, the Silky is a happy medium. His exercise needs are easily met.
Height/Weight: The Silky measure from 9-10 in (23-25 cm) at the shoulder and weighs from 8-10 lb (3.5-4.5 kg).
Coat: It is the lustrous coat that gives the breed its name. Fine in texture, the flat-lying coat is glossy and silky. The body coat ranges from 5-6 in (13-15 cm) in length and the Silky wears a rather profuse topknot on the top of the head.
Colour: The Silky is blue in colour with tan markings.
Grooming: Daily brushing of the fine coat is highly recommended.
Yorkshire Terrier:
Origin: A far cry from the diminutive glamorous breed of today, early Yorkshire Terriers were developed in the north of England in the mid-19th century for the job of dispatching rats in the coal pits and cotton mills. They were also featured combatants in rat-killing contests. But in those days, the breed was roughly twice the size of todayÕs Yorkies. ItÕs believed the Dandie Dinmont, Black and Tan and Skye Terriers were interbred to produce the original Yorkie. Then a cross to a Maltese reduced the breed in size. About that time, it began to be regarded as a Toy breed rather than a terrier; in 1886 it was given the breed name of Yorkshire Terrier. Breeding the attractive little Yorkies became a cottage industry in Yorkshire when the breed caught the fancy of wealthy ladies. The Yorkie has gone on to become one of the most popular Toy breeds.
Temperament: Even though the Yorkshire Terrier is often a very pampered pet, it is still loaded with spirit and displays its terrier heritage. It does make an alert watchdog.
Activity Level: Playful, bouncy and inquisitive, the Yorkie is an active dog that really doesnÕt know or care how small he might be. Its exercise needs are minimal, making it a good choice for stay-at-homes or couch potatoes. This is not a breed for small children.
Height/Weight: The dainty dogs should not exceed 7 lb (3 kg) in weight.
Coat: The long body coat is glossy, fine, silky and straight. Hair on the muzzle is very long.
Colour: The coat is steel-blue in colour, with tan head and legs. Pups are born almost black but their coats clear to blue by a year of age.
Grooming: Daily brushing is essential.
Hope this helps
