A Pilbara iron ore port was never designed for the exclusive use of Chinese company Citic Pacific, a lawyer for Clive Palmer's company Mineralogy has told the Federal Court.

The trial, which began today, revolves around control of the Cape Preston port, south-west of Karratha, which is part of the $12 billion Sino Iron project.

Mineralogy claims Citic is in breach of their agreement to hand over control of the port facilities after they were built.

Mr Palmer holds the tenements over the area but sold Citic the mining rights in exchange for an initial payment and ongoing royalty payments.

In court today, the WA Government argued the state be allowed to intervene in the trial because of its interests due to the project's State Agreement, which requires continuous exports of iron ore.

Justice James Edelman granted the intervention, despite Mineralogy's objection that the state's rights would not be affected by the case and it had no direct interest in the matter.

In court, Mineralogy's Simon Couper said Citic wrongly believed the port facilities were for their "exclusive occupation and control".

"This was not at any stage designed as a single user facility," he said.

"The respondents say 'this is ours, you keep out'."

Cape Preston Port in the Pilbara. ( Supplied: Citic Pacific )

Citic will argue Mineralogy's attempts to have it kicked off the port site are in breach of the State Agreement to maintain exports.

Citic also rejects Mineralogy's interpretation of the agreement between the two companies; it contends it was never intended Citic should build the port facilities and then hand them over to Mineralogy.

Justice Edelman will later this week visit the Sino Project site as part of the court case.

In court, Citic's Andrew Bell asked whether the parties should wear formal or casual attire on the bus tour.

"I certainly don't think that court robes (are necessary)," Justice Edelman responded.

Citic has invested billions in the port and mining infrastructure, and began exporting magnetite concentrate to Chinese steel mills in 2013.

The project is expected to have a final capacity of 24 million tonnes per year of the resource.