Costa Mesa-based Ceradyne Inc. has agreed to a sale to 3M Co. in St. Paul, Minn., for $860 million.
News of the buy sent Ceradyne’s stock up more than 42% during early trading today, to a market value of about $844 million.
The price is a 43% premium over Ceradyne’s closing price on Friday.
Ceradyne's board has recommended that shareholders accept the offer.
Ceradyne makes ceramics-based body armor and other products for the defense, industrial and commercial markets.
Ceradyne is the 25th-largest public company based in Orange County, with $572 million last year. It saw $83.9 million in 2011, and employs about 400 workers here and 2,400 overall.
3M makes a wide range of consumer and industrial products. It had $29.61 billion in revenue last year, with profit of $4.28 billion.
The deal for Ceradyne is 3M's biggest acquisition since its 2010 buy of Pasadena-based fingerprint identification systems maker Cogent Inc.
3M officials said in a statement they expect the acquisition to be completed this quarter.