Its around the size I'd have expected but I'm not the market....

Its around the size I'd have expected but I'm not the market. Its been clear for a while that they were likely to exceed the non-JORC historical estimate of 2.3Mt and it comfortably did this.

If you did really crude estimates like 1km strike * 200m down-dip * 10m average * 2.7 density you got to 5.4Mt (which unrealistically assumes a rectangle shape). The 4.5Mt is therefore close to this and the difference can be explained by bits being lost from the pit constraint and curved edges around the overall deposit.

Additionally, although a generous rate has been applied as a pit constraint, there are constraints meaning some edges of the deposit are excluded as they would require either underground mining or open pits that would not be economic at possible/probable prices. At some stage GT1 may do what Core modelled around Grants and have an initial open pit mine that extracts the majority of the resource with a small underground operation to access some remaining seams. If the economics work to do this, the JORC resource could increase.

What is does confirm is that there's several years of 1Mt/yr ore already known while further exploration continues.