As you are no doubt aware Bx is a subset of laterite, generally...

As you are no doubt aware Bx is a subset of laterite, generally that laterite which has a high enough alumina content to make it suitable for DSO or feedstock for refinery. Depends a bit on the crystalline form of the Bx, gibbsite etc, but Alcoas cutoff grade, last time I looked was about 28% giving head grade of about 32.5% total Al2O3. The area in question was part of original Alcoa lease but excised when they reduced the size of the lease to gain permission to gain access to a couple of high quality forest blocks near Dwellingup, many years ago. Hence no viable Bx around the north end of the range, which is why BRL ceased to exist