An associate of former Labor minister Eddie Obeid has struggled to tell a corruption inquiry how he knew there were coal deposits in the Bylong Valley before he bought a farm there.

The Independent Commission Against Corruption (ICAC) is investigating allegations the Obeid family and their associates stood to profit by around $100 million from inside knowledge about mining licences in the area.

It is alleged the information came from former mining minister Ian Macdonald or from staff in his office.

Counsel-assisting the inquiry Geoffrey Watson put his head in his hands during evidence given by Obeid family associate Rocco Triulcio.

Commissioner David Ipp told Mr Triulcio he was wasting time by guessing with his answers.

Mr Triulcio was a star witness at last week's inquiry into the $10,000 discount former Labor minister Eric Roozendaal received on a car from the Obeid family.

Today he was back on the stand, but at first said he could not recall paying a $300,000 deposit on a farm for the Obeid family in the Bylong Valley.

"It could have been (that) we directed some of the money towards it, but we didn't fund it," he said.

"I don't do the accounts."

Laughter erupted in the public galley when the animated witness said he bought a farm next door to the Obeid property because it had dams, a bore and a lot of grass.

There was even more laughter when he told the inquiry that he could not recall the name of his own property and had never done any work there.

Mr Triulcio said he registered the farm under someone else's name because he was "away on his honeymoon".

He also admitted that he had only been to his farm once or twice in the past four years.

No rats

Sorry, this video has expired ICAC seeks answers for $100m property windfall

Mr Triulcio admitted he knew there was coal in the area before buying the farm but gave the inquiry conflicting answers about how he knew that.

There was much disappointment in the packed public gallery when he was stood down.

His brother, Rosario Triulcio, was then questioned about their farm and denied that he was fabricating his answers.

When asked about stock that may have been kept on farms in the Bylong Valley area, Rosario Triulcio said he was sure it did not include rats.

Mr Ipp then replied: "Not four-legged ones, anyway."

During the lunch break, the Triulcio brothers avoided the media by going into a shopping arcade and a Chinese restaurant.

Earlier today, Obeid family lawyer Gregory Skehan told the inquiry he had agreed to become the sole shareholder and director of an Obeid-owned company called Voop, but that he could not recall why.

He said at the time he did not know the family had inside knowledge or was using him to conceal their involvement in mining transactions.

The inquiry has also heard that former Labor mining minster Ian MacDonald, who is accused of making decisions that benefitted the Obeid family, may have breached ICAC rules by phoning his business partner John Gerathy after being questioned by investigators ahead of the ICAC proceedings.