I was poking around in the LHS and came across a bag of Woodlands Scenics 'gravel', a product I was not aware of. It's intended for modelling gravel roads and such, but I bought a bag if 'fine grey' for a test patch on the layout. This product is a mineral material, not the usual ground walnut shells so it wets easily with ordinary water and stays in place. The 'fine' grade is seemingly perfect for N scale. There are only two colours available, buff and light grey, each in 'fine' and 'coarse'. The light grey might be a little too light for me and it could be a little greyer as it has a slight 'buffy' tone. There is a slight variation in the coloration of the individual particles, so it's not too monochromatic, but it avoids the 'salt and pepper' look. I might experiment with a little grey wash to see if I can nudge it a little closer to what I am aiming for, but otherwise I'm very satisfied.
So this begs the question: If WS can produce a quality mineral based gravel, why don't they produce a quality mineral based ballast, with a wider range of colours and textures?
Geoff