Australian mining major Rio Tinto Monday, March 16, offered 59%-Fe Supplementary Product, or SP10, iron ore fines via spot tender, but interest appeared limited as the alumina content was much higher than that of other mainstream Australian products.

The cargo contains 4.9% alumina, around double Rio Tinto’s flagship Pilbara Blend fines at 2.5% alumina and BHP Billiton’s liquid medium grade products, Newman fines and Mining Area C fines, at 2.3% alumina.

“There won’t be mills too willing to buy such high alumina material as it causes the reaction time in blast furnaces to speed up to a point where we can’t control production well,” said a source at a Chinese steelmaker that received the tender.

Extremely high alumina content results in slag becoming excessively fluid during the steelmaking process, sources said earlier.

Another trader who received the tender said high alumina material like SP10 could potentially be blended with low alumina product like Brazilian Iron Ore Carajas fines produced by Vale.

“From a production cost perspective this may make sense for mills, but I doubt anyone would want such high alumina ore when environmental regulations are so strict,” the trader said.

Another trader said it “would not be easy to find buyers” for the SP10 fines cargo when the Chinese government was tightening emissions restrictions for steelmakers.

Market sources were wary of putting a price adjustment value on such high alumina material, with one end-user suggesting $1.50/dmt for every 1% of alumina for 60-63.5%-Fe ores containing above 2.5% alumina was possible.

A Rio Tinto official would not provide further details on the tender, saying only it was “not a deviation from main core products” and “this product does get produced every now and then and we will look to sell this product.”

The miner last offered SP10 fines on March 27, 2014, via fixed price spot tender, Platts data showed. The tender was not heard to have been awarded.

Not all of Rio Tinto’s regular customers received the invitation to bid for the SP10 fines cargo Monday.

Aside from 4.9% alumina, the SP10 fines cargo also contains 5.5% silica, 0.075% phosphorus, 0.02% sulfur, 4.3% loss on ignition and 5% moisture.

The 170,000 mt shipment will load March 30-April 8.

Sources said Rio Tinto has invited floating price bids to be submitted on a dry metric ton unit FOB basis against the April average of the Platts 62% Iron Ore Index assessment minus the Baltic Exchange C5 Index rate.

The spot tender closes 4 pm Beijing Time (0800 GMT) Monday.