Rio Tinto Group stood out among its peers in a roller-coaster second quarter of iron ore production amid volatile commodity pricing, according to S&P Global Market Intelligence data.

Iron ore prices fell in May due to weak demand, followed by a brief price rally stemming from the easing of Shanghai's COVID-19 lockdown restrictions in early June. Then government stimulus to boost China's flagging economy was halted later that month by Beijing's own COVID-19 outbreak.

"While there is lots of optimism about demand recovering through next year, the near term doesn't look that great for demand for steel production and therefore iron ore, so supply will be the critical mix," Westpac bank senior economist Justin Smirk told S&P Global Commodity Insights.

"If iron ore supply continues to improve from here, then that's a negative for prices, and we've already seen that recently as prices held up due to tightness in supply," Smirk said.

Rio Tinto's 68.6 million tonnes of iron ore production in the second quarter was 3.6% more than the year-ago period and 9.9% more than the first quarter, a feat none of its top-five major peers could manage.

Vale SA still produced the most iron ore in the period with 74.1 Mt, up 17.4% from the prior quarter while decreasing by 1.2% year on year. Similarly, BHP Group Ltd.'s 64.2 Mt of iron ore output for the second quarter was up 7.5% from the first quarter but down 1.7% compared to the year-ago period.

Australia's GWR Group Ltd. achieved the largest year-over-year and quarter-over-quarter increases, with iron ore output jumping by 86.4% and 153.2%, respectively. Production levels at the company's C4 iron ore operations in Western Australia continued to improve from past record volumes, after huge growth in the first quarter.

Metinvest BV recorded the biggest decreases in iron ore production, down 66.8% year over year and 56.3% quarter over quarter. The mining company's owner, Rinat Akhmetov, reportedly planned to sue Russia as of May for up to $20 billion in losses over the country's invasion of Ukraine. Russian forces' bombing and shelling hit Metinvest's facilities in Mariupol.

Second-quarter iron ore output from Australia's Fortescue Metals Group Ltd. rose 14.7% over the first quarter, when the Australian miner suffered along with the rest of its top-five iron ore peers as prices dipped. The company's quarterly iron ore production decreased by 8.8% year over year.

Fortescue produced 5.7 Mt less than the year-ago quarter, which was the biggest loss among the top-20 iron ore miners over the period.

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