How much silver is in a US half dollar?

Answer 1

Barber, Walking Liberty, Franklin, and 1964 Kennedy halves weigh 12.5 gm and were made of 90% silver, so they contain 11.25 gm of pure silver.

1965-70 Kennedy halves weigh 11.5 gm and are 40% silver so they contain 4.6 gm of silver.

All modern circulation halves are made of copper-nickel and have no silver in them.

Some 1776-1976 Bicentennial halves were struck in 40% silver and sold in special collectors' sets. Since 1992, "Prestige" half dollars have been made in the old 90% silver alloy but these are also only available to collectors and aren't intended for spending.
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By the early 1960s the rising price of silver was nearing the point where the bullion value of United States silver coins would exceed face value. In 1965, the U.S. introduced layered composition coins made of a copper core laminated between two cupro-nickel outer faces. The silver content of dimes and quarters was totally eliminated, but the Kennedy half dollar composition still contained silver (reduced from 90 to 40 percent) from 1965 to 1970.

The 1964 Kennedy halves were massively saved out of circulation for sentimental reasons. Those issued through the end of the 1960s were hoarded as the only precious metal U.S. coins remaining in production, and as the price of silver continued to rise pre-1964 halves disappeared from circulation as well. By the time that the coin's composition was changed to match that of the clad dimes and quarters in 1971, both businesses and the public had adapted to a country in which the half dollar did not generally circulate. The quarter took over the half's role as the highest-value component of change.