More comments from a second reading of the file...

More comments from a second reading of the file https://fintel.io/doc/sec-albemarle-corp-915913-ex961-2023-february-15-19403-3937

The 72.5 % recovery at Greenbushes was obtained at the Technical Grade Plant (TGP).

Chemical Grade concentrates are being produced at two different Plants: CGP1 and CGP2. CGP1 is a mature plant with ball mills and 72.1 % recovery. The CGP2 was commissioned in 2019-2020, put in C&M and restarted again in 2021. CGP2 used the experience acquired with CGP1, but the ball mill in the latter has been replaced with a High Pressure Grinding Rolls mill (HPGR) in CGP2. The reasons are lower costs and better efficiency.
The recovery in CGP2 has increased from 50.5 % in May 2021 to 68.2 % in Q4CY2022 vs a predicted recovery of 75.4 %. They found that the amount of slimes (very fine-grained ore that goes to waste) produced has been higher than expected. Nevertheless, two more processing plants CGP3 and CGP4 are being built with HPGRs and not ball mills.

For those interested, here you have the features of both HPGR and SAG mills from Metso, the company that produced the SAG mill at Kathleen Valley:

https://www.metso.com/portfolio/hrc-series/
https://www.metso.com/portfolio/premier-mills/

From the rationale of both systems, I'd expect the amount of slimes to be lower in a SAG mill compared to a HPGR mill. That is because of the friction between the metal rods and the ore in the HPGR. This friction of ore against harder material (metal) does not happen in SAG mills.