Tip of a thin cone
In this photo of a thin cone tip the grain size can be seen.  Each micronometer division is 0.1mm, close
to the apparent grain size.  The grains, although not well seen here, look to be subrounded and relatively
quartz rich.

Tip of a fat cone.
This view of a fat cone tip shows the fat cone's poorer sorting, lower quartz content and in this case,
slightly smaller grain size.