Silver mining company stocks posted big gains Friday on the back of a hefty surge in silver's price and renewed fears that the U.S. may be headed for a double-dip recession.

Economists were expecting employers to add between 70,000 and 90,000 jobs, a number that would have left the nation's unemployment rate at 9.1 percent. But instead the world's biggest economy added zero nonfarm jobs. In July, at least, employers had added 85,000 jobs.

Net employment flatlined in August, Ellen Zentner, a senior U.S. economist at Nomura Securities International Inc. in New York, who forecast a decline of 5,000, told Bloomberg. When the outlook is uncertain, businesses don't hire. Calls that we're on the cusp of a recession or already there are not completely unwarranted. 

The Labor Department report, coming on the heels of recent downbeat data, reinvigorated worries about a double-dip recession: On Wednesday a private report said the U.S. private sector created 91,000 jobs in August, also short of expectations; on Thursday data showed initial jobless claims were still at a lofty 409,000; and consumer confidence dropped last month to a two-year low.

On the futures market silver settled a stunning 3.7 percent higher on the CME Comex division of the New York Mercantile Exchange. That lifted stocks and exchange-traded funds that are backed by physical silver.

In late afternoon trading, the iShares Silver Trust rocketed up 4 percent, while miners also jumped: Silver Standard Resources Inc. vaulted 5.7 percent, Endeavour Silver Corp. climbed 3.2 percent and Pan American Silver Corp. jumped 2.8 percent.

Gold and gold-related assets climbed as well Friday though not quite as strongly as silver and silver-related assets.

BMO analyst Andrew Kaip said silver's relatively superior strength emerged recently when gold was falling.

Silver has been holding up very well above the $40 an ounce level. It has held its ground better than gold did the last two weeks when gold gave up some gains, he said.

He also noted that smaller gold mining companies, known as juniors, were posting gains on par with silver and silver mining companies.