There are no rare dates among quarters minted since the 1940s. You have to go much farther back to find anything that's truly valuable, although there are some pretty expensive quarters from the first third of the 20th century. Here's a few representative prices as of 11/2010:
Most silver US quarters are not rare or even scarce, but it depends on the DATE of the coin, post new question.
There is no such thing as pure silver quarters, there are 90% silver quarters which are dated 1964 and earlier though in the US.
1964 was the last year US quarters were made of Silver.
All pre-1965 US quarters and dimes are 90% silver.
All US quarters dated 1964 or before are 90% silver.
The last year for silver quarters was 1964.
No, only the only US quarters intended for circulation with silver in them are US quarters dated 1964 and earlier.
Nevada and Alaska
1965. Any US quarters dated 1964 or earlier are 90% silver.
1964 was the last year the US produced silver quarters for circulation.
No 1972 US quarters have silver in them, the last year for silver quarters was 1964. so spend it
No US quarters were struck in silver in 1967, 1964 was the last year for silver quarters put into circulation.