One of the "well-connected entrepreneurs" granted a lucrative mining licence by former NSW minister Ian Macdonald couldn't wipe the smile off his face after signing the deal over a magnum of pinot noir, an inquiry has heard.

"I can't wipe the smile off my face, merry bloody Christmas," an email from Craig Ransley reads.

The NSW Independent Commission Against Corruption (ICAC) is probing whether the former mines minister gave an improper benefit to former union boss John Maitland and his associates Mr Ransley and Andrew Poole, relating to the licence allocated to Doyles Creek Mining in the NSW Hunter region in December 2008.

Mr Macdonald had no basis to "essentially gift" the licence worth tens of millions of dollars to the group, the inquiry heard on Monday.

The ICAC's Operation Acacia is also looking at whether Mr Macdonald took improper steps to overcome departmental advice and if he concealed any improper behaviour.