Journal of the Royal Society of Western Australia, 86(2), June 2003 
Figure 7. A,B: Optical photomicrographs of coarse sand-sized quartz grains in granitic upper saprolite. Note biotite inclusions (B), holes 
(H), and attachments of opaque minerals (O). C,D: Optical photomicrographs of coarse sand-sized quartz grains in the Westonia 
Formation. Note large proportion of fractured, etched, monocrystalline grains without holes, mineral inclusions or attachments, 
produced by repeated cycles of erosion, transport, deposition and alteration (weathering, pedogenesis) before being incorporated into 
the Westonia Formation. A,B = sample YN41 26.1 m, C = sample EY61/1, D = sample YN41 7.0 m; A,C cross-polarized light; B,D plane- 
polarized light. 
Lithic characteristics. The Westonia Formation is 
subdivided into the following three major lithofacies, 
based primarily on differences in induration, overall 
grain-size distribution, quartz granulometry and the 
extent of nodule and pisolith development. 
1. Clayey sand lithofacies. This forms the base of the 
Westonia Formation and is either overlain by the 
bimodal sand lithofacies (Table 1), or directly by 
the nodular sandstone lithofacies (Table 2, Fig 8A). 
It typically comprises yellow to light red, poorly 
indurated, framework to matrix supported, clayey 
medium to coarse quartz sand. Where exposed at 
the landsurface, as in the face of breakaways, the 
material becomes well indurated forming a clayey 
sandstone. Matrix (<63 pm) material is dominantly 
highly disordered kaolinite with lesser gibbsite, 
goethite and X-ray amorphous minerals. 
Framework quartz grains are typically unimodal, 
coarse, poorly sorted, mesokurtic and fine skewed 
(Fig 5). In contrast to granitic saprolite, the quartz 
grains are nearly all monocrystalline, strongly 
etched and free of inclusions (Fig 7C,D). 
Roundness within the coarser quartz grains is 
distinctly bimodal, comprising a primary mode of 
very angular to sub-angular grains and a smaller 
secondary mode of rounded to well-rounded 
grains (Fig 9A-C). The rounded quartz grains are 
severely pitted (Fig 9C) making them more opaque 
(milky coloured) than the more angular quartz 
grains when viewed in hand specimen. 
2. Bimodal sand lithofacies. This lithofacies is only 
locally developed and where present crops out at 
the landsurface or occupies a middle position 
between the clayey sand and nodular sandstone 
lithofacies. It comprises yellow, loose to poorly 
indurated, framework supported, clayey bimodal 
coarse and fine quartz sand (Fig 5). Except for 
having thin coats of goethite-impregnated kaolin, 
the quartz grains have similar external and internal 
properties to the clayey sand facies. Small 
quantities of fine sand-sized, spherical to ovate 
bodies of goethitic kaolin with an internal pelletal 
or oolitic fabric ("kaolin spherites" of Killigrew & 
Glassford 1976), are also commonly present. 
Matrix material is dominantly highly disordered 
kaolinite with minor goethite and gibbsite. 
3. Nodular sandstone lithofacies. This forms the 
uppermost part of the Westonia Formation at East 
Yornaning and typically comprises grey to red, 
well indurated, nodular to incipiently pisolitic, 
medium quartz sand (Fig 8B). Framework quartz 
grains are mostly weakly unimodal to polymodal, 
medium to fine, poorly sorted, platykurtic, and 
fine to coarse skewed (Fig 5). Rounded quartz once 
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