US producer Arch Coal has commenced a $500m unsecured notes offering to raise funds to help with the purchase of the $761m Jacobs Ranch complex.

The acquisition is expected to be completed in the third quarter of 2009 and the principal amount of senior unsecured notes will be due in 2016.

The proceeds from the offering would be used for general corporate purposes including financing future acquisitions of the Wyoming-based mining site, Arch Coal said.

Arch Coal’s subsidiaries would guarantee the indebtedness under the company’s existing senior secured credit facility, according to the company.