US Mint to Stop Making 90% Silver Coins

The United States Mint just received an early Christmas present. The agency was gifted the freedom to increase the purity of its 10-cent, 25-cent and 50-cent silver coins.

Until President Obama signed the FAST Act into law on Friday, Dec. 4, the U.S. Mint had to produce silver coins for numismatic products like annual proof sets in a composition of 90 percent silver and 10 percent copper. The Mint for years has wanted to make them in .999 fine silver. It now has that authority with tweaks throughout U.S. coinage law that replaced the traditional 90/10 language with "not less than 90 percent silver." The changes open the door for higher purity coins and the Mint plans on walking through it.

CoinNews expects to hear from Mint officials soon on when the move to .999 happens. The decision is not as cut and dry as expected. The San Francisco Mint had already started striking 2016-dated silver coins in the 90/10 mix before our last visit in October. The Mint would have to scrap those, which would seem unlikely, continue to make them along with .999 fine examples, or simply wait and make the changeover in 2017 or later.

A 90% silver and 10% copper ratio is often referred to as "coin silver." The 90/10 mixture was a mainstay of U.S. circulating coins from the early 1800’s until the Coinage Act of 1965 became law. Its use returned in 1982 for modern commemorative coins and in 1992 with the introduction of annual Silver Proof Sets.

The new mandate does not apply to commemoratives, but legislation for recently proposed silver dollars has included the more flexible composition language.

Advantages of .999

There are several benefits in moving to more pure silver. As examples, when the U.S. Mint compared manufacturing data between the 2012 Infantry Soldier Silver Dollar in 90% silver and its .999 fine 2013 Proof American Silver Eagle, the following differences were discovered:

National Infantry

(90/10 Alloy) American Eagle Silver (0.999 Silver) Comments Die Life (coins per die) 600 coins 1800 coins 3X better with 0.999 Silver Scrap (Haze related) 14% avg 10% avg 4% better with 0.999 Silver Customer Returns 2% avg 1.3% avg 0.7% better with 0.999 Silver Downtime (Cleaning dies) 80X/day 20X/day 4X less downtime with 0.999 Silver

In terms of quality, the Mint has found that the copper in 90/10 alloy exceeds the maximum solubility of copper in silver and can cause coin spots and hazing, which drives higher scrap rates and customer returns.

The "excess copper precipitates out of solution and can cause a build up on the dies or could cause a harder blank surface," a Mint document describes. "The finished product displays varying amounts of breakup spots and haze."

.999 silver also flows better under pressure. That results in superior fills and fewer strikes to make collectible coins.

The U.S. Mint indicates that while the material cost is lower for 90/10 alloy, the efficiency, quality and manufacturing improvements gained from .999 fine silver are offsetting. There is also a larger supply base for .999 fine silver blanks since they are easier and cheaper to fabricate then custom-made .900 fine silver blanks.

The FAST Act includes other coin-related provisions like edge lettering for 2016 Silver Eagles and a stronger call for one-ounce coins in .9995 fine palladium.