Weight of a quarter is 5.670 g
And did you know that if you take the weight of a dime (2.268 g) it is 10/25 the weight of a quarter? And the weight of a half-dollar (11.340 g) is twice the weight of a quarter?
That means their mass is in direct proportion to their value. (Note: this doesn't follow for the penny and the nickel).
The cool thing about this is that $20 worth of dimes, quarters and/or half-dollars would all have the same mass, regardless of the mixture of coins. And since they have the same density, a bucket filled with dimes, or quarters, or half-dollars (or a mixture) would nominally have the same value (discounting packing differences).
There is more information on the U.S. quarter on Wikipedia, link given below.
