IGO has been undertaking a strategic review in an attempt to revaluate its resources.
The American Exploration & Mining Association was joined by a coalition in filing a challenge last Friday in the Wyoming district court.
The world's largest producer of iron ore shipped 80.3 million tons of the steel-making commodity in the quarter.
Chile's financial regulator had allowed a planned lithium joint venture between SQM and Codelco to proceed without a vote by SQM shareholders.
