Size/grade of HO ballast?

[RobertInOntario]

You might experiment on some hidden track to see what looks good. CN locally seems to have a mixture -- bigger chunks in the middle and fine at the edges but that was in a station.
I think that it may be laid as large chunks and get broken down over the years. I think ballast is one of those features that need to look right rather than be scale.

Ballast also varies a lot, even within one section of track. So you don't have to worry a whole lot about being overly consistent. Rob