Feb 21 (Reuters) - Australia's mining chemicals maker Orica said on Wednesday it will acquire the entire stake in U.S.-based sodium cyanide manufacturer Cyanco Intermediate 4 Corp for $640 million.

Orica will fund the acquisition via an underwritten institutional placement worth A$400 million ($261.88 million), it said. ($1 = 1.5274 Australian dollars) (Reporting by Poonam Behura; Editing by Shailesh Kuber)