Green Critical Minerals, page-41

Some things to note here.

1. There are two principal types of REE ore -
First the phosphate type where the REEs are bound into phosphate minerals like monazite. eg My Weld.
https://en.wikipedia.org/wiki/Monazite
Second the clay hosted ores where REEs which have been weathered out of the primary intrusives are washed into clay beds and the REE minerals are selectively bound to the surface (adsorption) of the clay units, or into the inner layers (absorption) of the clay units.
See briefly:- https://www.nature.com/articles/s41467-020-17801-5 From which this diagram:-



Interesting to note why clay is so slippery - the clay units (large crystals !!) are flat and with a bit of water slide over each other.


2. The mining and processing of the phosphate rock ores, Mt Weld and the NT equivalents, is difficult. Not least because they contain Thorium and hence yield a radioactive waste. This is the ore type you refer to, taking many years to get to market.
Of course later 'copycats' will benefit from earlier tech work.

3. Clay hosted ionic adsorption REE ores are much easier to mine and process - sometimes the mining can be done in situ, by just circulating the reactant through the clay in the ground - done in China.
The adsorbed REE material is released by ion-exchange and common cheap reactants are used eg common salt.

4. However if the REEs are absorbed into the clay, strong expensive reactants are needed eg strong acids, to break open the clay structure. This is usually uneconomic.

So the magic bullet is a large high grade near surface deposit of ionic adsorption metals.

That becomes a lottery when the deposit is first discovered and offered to the market. There are lots in Oz yet to be proven up, but also a lot of research, some publicly funded, on improving the chances of economic success.

IMO if you want a Rare Earths play you should chose a company with other hot irons in the fire. Does GCM meet that criteria ?? For you to decide.

GL.