Dredge mining of dunal deposits has been less frequent in Iluka’s resource inventory. It has, however, been a part of Iluka’s mining and operational experience, both in the United States and Australia. An example is North Stradbroke Island, where Iluka had a 51 per cent interest in the then operator, Consolidated Rutile Limited.
Dunal deposits are typically very large deposits, principally formed as a consequence of wind action. Wind willows away the lighter sand leaving a progressive higher grade zone of valuable heavy mineral (VHM). Dunal deposits are often tens of kilometres long, the width can be a few kilometres and the thickness can be up to 100 metres.
- At North Stradbroke Island, mining occurred at a dune thickness of about 130 metres. HM grade was, however, low at about half a percent to about 0.7 per cent HM.
Dunal deposits can be up to 200 million tonnes of HM or more and because of typical gradational boundaries, they are amenable to bulk (dredge and hydraulic) mining.