In sedimentary kaolin deposits either in-situ or reworked by alluvial-fluvial-colluvial processes feldspar (is relic) wackes may exist. The terrigenous evinronment used to be barren as to fossils because the parent rocks underwent pervasive chemical weathering under tropical conditions.
See:
DILL, H.G. (2016) Kaolin: soil, rock and ore From the mineral to the magmatic, sedimentary, and metamorphic environments.- Earth Sciences Reviews 161: 16-129.
DILL, H.G. (2010) The “chessboard” classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium.- Earth Science Reviews, 100: 1-420. [see silica]