Nanomorphological structure of well-crystallized Georgia and poorly cr
ystallized North Queensland kaolinite particles have been compared usi
ng field emission scanning electron microscopy (SEM) and atomic force
microscopy (AFM). In general, there is good agreement in information f
rom the 2 very different imaging techniques. AFM gives more detailed i
nformation on step and ledge dimensions, microvalleys and crystallogra
phic orientation of irregularities on basal planes and edges of the cr
ystallites. There are major differences in nanomorphology and surface
structure between the 2 kaolin samples with the Georgia kaolin showing
200-500-nm, relatively flat basal planes with some cascade-like step
growth 50-100 nm wide. The edges, apparently flat and right angled in
SEM images, appear beveled in AFM images due to artifacts from the asp
ect ratio of the AFM tip. The North Queensland kaolinite has much more
complex surface structure with anhedral crystallites attached to larg
er particles, high density of steps and nm-scale irregularities (often
crystallographically directed).The additional step edge site contribu
tion from the attached crystallites is estimated as a minimum of 6%, g
iving a total edge contribution above 30% of the kaolinite total surfa
ce area. These structures will generate a substantial pH-dependent cha
rge across the surfaces of the North Queensland kaolinite platelets. A
n idealized, uniform, pH-independent, negatively charged basal plane c
annot be assumed from these structures. There is also some evidence, f
rom both SEM and AFM images, of curvature in the thinner, poorly order
ed structures of the North Queensland kaolinite particles.