Specialty chemicals firm Ferro Corp. (NYSE: FOE) has received an unsolicited buyout offer from A. Schulman Inc. (NASDAQ: SHLM), another provider of specialty chemicals and plastics. The total value of Schulman’s offer is about $563 million, or $6.50 a share, of which half will be paid in cash and half in A. Schulman common stock.

According to A. Schulman’s press release, the offer represents a 25% premium to Ferro’s closing price on Friday and a 32% premium over the volume-weighted average trading price for the past 60 days. Including debt, A. Schulman’s offer totals $855 million.

A. Schulman said its offer was based on publicly available information for the first nine months of Ferro’s 2012 fiscal year. In February, Ferro rejected an offer from A. Schulman that had expressed its “strong intent” to combine with Ferro.

Shares of Ferro are up 30% in the first half-hour of trading this morning, at $6.76 after hitting a new 52-week high of $6.82 earlier. The prior 52-week range was $2.38 to $6.39.

A. Schulman’s shares are also trading higher, up 1.4% at $31.55 in a 52-week range of $17.75 to $33.40.