New process could unlock untapped US ilmenite supplies

Published: Friday, 07 July 2017

A pilot scheme in the USA, jointly funded by the state government of Minnesota and the University of Minnesota, has delivered pigment-grade titanium dioxide at up to 99.8% purity from large ilmenite deposits that were previously considered unusable.

A pilot scheme has delivered pigment-grade titanium dioxide (TiO2) from the large ilmenite deposits in the US state of Minnesota, which were previously considered unsuitable for commercial use due to the presence of hard-to-remove contaminants.

The Natural Resources Research Institute, part of the University of Minnesota, announced on May 25 that high-quality titanium dioxide had been extracted through a proprietary process which is suitable for commercial application.

The pilot scheme, joint-funded by the Minnesota state government and the University of Minnesota, has delivered pigment-grade titanium dioxide at up to 99.8% purity, processed from 10 tonnes of local ilmenite.

Ilmenite reserves

A band of ilmenite deposits runs along the northeastern edge of Minnesota. There are at least 13 oxide-bearing bodies in the region.

Among these is Longnose deposit, owned by mining junior American Shield Titanium Group, reported to be among the largest and highest quality ilmenite deposits in the US, which delivered the ilmenite used in the pilot.

Drilling at Longnose indicates about 58m tonnes ilmenite with 17% TiO2 content, according to the Minnesota Minerals Coordinating Committee (MMCC).

Of the other two sites that have been defined, the Titac deposit has around 45m tonnes at 15% TiO2, while the Water Hen deposit has some 62m tonnes at 14% ilmenite, the MMCC said.

Cost-effective process

Exploitation of the deposits has been so far prevented by the high proportion of magnesium oxide in the ore, which is hard to remove and compromises the whiteness of the finished product.

But the pilot demonstration was able to produce high-purity TiO2 through the use of proprietary hydrometallurgical processing.

The process also delivers usable 98.5% pure iron oxide.

Speaking to IM, the NRRI initiative director George Hudak noted that the process also left other minerals as byproducts, such as vanadium and magnesium. These could potentially be extracted as well.

Hudak said that the production system was a "closed loop", meaning that, in theory, it could be carried out with little environmental impact.

"This process (...) appears to be very cost-effective and with commercial potential," said American Shield boss Bill Ulland.

The cost of developing a mine and mill on the Longnose site is estimated at $170m, Ulland told IM.

Ulland said that the next step in exploiting the deposit would be to find a partner to handle the extraction.

The region of Minnesota in which Longnose is found is already a centre of iron oxide mining, and the reserve appears easily minable, with a low sulphur content which does not create the same pollution risks as in other nearby copper deposits.

"Access is not a problem (…) I don’t think you could find a better place [for a deposit]," he said.