Alteration is nonexistent to very weak at best and the weak chlorite and sericite are believed to be mainly post-ore effects.
en.wikipedia.org Sericite is a common alteration mineral of orthoclase or plagioclase feldspars in areas that have been subjected to hydrothermal alteration typically associated with copper, tin, or other hydrothermal ore deposits.
en.wikipedia.org The geometry of the prospect is unresolved, but appears to contain stacked, broadly east-west trending zones that host sheeted to massive quartz-carbonate veining in sericite altered meta-sediments.
www.proactiveinvestors.com.au Structurally, brammallite is quite similar to muscovite or sericite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer potassium.
en.wikipedia.org Beginning in 1951, the deposit was mined for associated sericite, which was used as a white filler.
en.wikipedia.org